Video coding with unfiltered reference samples using different chroma formats

ABSTRACT

A device for processing video data includes a memory configured to store video data and one or more processors implemented in circuitry. The one or more processors are configured to obtain unfiltered reference samples for an area of a picture of the video data. The one or more processors are configured to disable intra-reference sample smoothing of the unfiltered reference samples for chroma samples in a YUV 4:2:0 format and in a YUV 4:4:4 format. The one or more processors are further configured to generate, using intra-prediction, chroma samples of a predicted block for a block of the picture based on the unfiltered reference samples when generating the chroma components in the YUV 4:2:0 format and when generating the chroma components in the YUV 4:4:4 format.

This Application claims the benefit of U.S. Provisional PatentApplication 62/819,368, filed Mar. 15, 2019, the entire content of whichis hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to video encoding and video decoding.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,so-called “smart phones,” video teleconferencing devices, videostreaming devices, and the like. Digital video devices implement videocoding techniques, such as those described in the standards defined byMPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced VideoCoding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), andextensions of such standards. The video devices may transmit, receive,encode, decode, and/or store digital video information more efficientlyby implementing such video coding techniques.

Video coding techniques include spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (e.g., a video picture or a portion of a video picture) maybe partitioned into video blocks, which may also be referred to ascoding tree units (CTUs), coding units (CUs) and/or coding nodes. Videoblocks in an intra-coded (I) slice of a picture are encoded usingspatial prediction with respect to reference samples in neighboringblocks in the same picture. Video blocks in an inter-coded (P or B)slice of a picture may use spatial prediction with respect to referencesamples in neighboring blocks in the same picture or temporal predictionwith respect to reference samples in other reference pictures. Picturesmay be referred to as frames, and reference pictures may be referred toas reference frames.

SUMMARY

In general, this disclosure describes techniques for supportingdifferent chroma formats in video codecs.

In one example, a method of processing video data includes: generating,by one or more processors implemented in circuitry, a coding unit for achroma component of a block of video data in a YUV 4:4:4 format or in aYUV 4:2:0 format; splitting, by the one or more processors, the codingunit for the chroma component into a first triangle-shaped partition anda second triangle-shaped partition based on enabling of a triangularprediction unit mode; and applying, by the one or more processors, pixelblending using a set of weights for the YUV 4:2:0 format to generate apredicted block for the chroma component when the one or more processorsgenerate the coding unit for the chroma component in the YUV 4:2:0format and when the one or more processors generate the coding unit forthe chroma component in the YUV 4:4:4 format, wherein applying pixelblending comprises determining weighted averages, using the set ofweights for the YUV 4:2:0 format, of collocated motion compensatedpixels of the first triangle-shaped partition and the secondtriangle-shaped partition based on motion information of the firsttriangle-shaped partition and the second triangle-shaped partition,respectively.

In another example, a device for processing video data includes: amemory configured to store video data; and one or more processorsimplemented in circuitry. The one or more processors are configured to:generate a coding unit for a chroma component of a block of video datain a YUV 4:4:4 format or in a YUV 4:2:0 format; split the coding unitfor the chroma component into a first triangle-shaped partition and asecond triangle-shaped partition based on enabling of a triangularprediction unit mode; and apply pixel blending using a set of weightsfor the YUV 4:2:0 format to generate a predicted block for the chromacomponent when the one or more processors generate the coding unit forthe chroma component in the YUV 4:2:0 format and when the one or moreprocessors generate the coding unit for the chroma component in the YUV4:4:4 format, wherein, to apply pixel blending, the one or moreprocessors are configured to determine weighted averages, using the setof weights for the YUV 4:2:0 format, of collocated motion compensatedpixels of the first triangle-shaped partition and the secondtriangle-shaped partition based on motion information of the firsttriangle-shaped partition and the second triangle-shaped partition,respectively.

In one example, a computer-readable storage medium includes storedthereon instructions that, when executed, cause one or more processorsto: generate a coding unit for a chroma component of a block of videodata in a YUV 4:4:4 format or in a YUV 4:2:0 format; split the codingunit for the chroma component into a first triangle-shaped partition anda second triangle-shaped partition based on enabling of a triangularprediction unit mode; and apply pixel blending using a set of weightsfor the YUV 4:2:0 format to generate a predicted block for the chromacomponent when the one or more processors generate the coding unit forthe chroma component in the YUV 4:2:0 format and when the one or moreprocessors generate the coding unit for the chroma component in the YUV4:4:4 format, wherein the instructions that cause the one or moreprocessors to apply pixel blending cause the one or more processors todetermine weighted averages, using the set of weights for the YUV 4:2:0format, of collocated motion compensated pixels of the firsttriangle-shaped partition and the second triangle-shaped partition basedon motion information of the first triangle-shaped partition and thesecond triangle-shaped partition, respectively.

In another example, a device for coding video data includes: means forgenerating a coding unit for a chroma component of a block of video datain a YUV 4:4:4 format or in a YUV 4:2:0 format; means for splitting thecoding unit for the chroma component into a first triangle-shapedpartition and a second triangle-shaped partition based on enabling of atriangular prediction unit mode; and means for applying pixel blendingusing a set of weights for the YUV 4:2:0 format to generate a predictedblock for the chroma component when the one or more processors generatethe coding unit for the chroma component in the YUV 4:2:0 format andwhen the one or more processors generate the coding unit for the chromacomponent in the YUV 4:4:4 format, wherein the means for applying pixelblending comprises means for determining weighted averages, using theset of weights for the YUV 4:2:0 format, of collocated motioncompensated pixels of the first triangle-shaped partition and the secondtriangle-shaped partition based on motion information of the firsttriangle-shaped partition and the second triangle-shaped partition,respectively.

In one example, a method of processing video data includes: obtaining,by one or more processors implemented in circuitry, unfiltered referencesamples for an area of a picture, wherein the one or more processors areconfigured to disable intra-reference sample smoothing of the unfilteredreference samples for chroma samples in a YUV 4:2:0 format and in a YUV4:4:4 format; and generating, by the one or more processors, usingintra-prediction, chroma samples of a predicted block for a block of thepicture based on the unfiltered reference samples when generating thechroma components in the YUV 4:2:0 format and when generating the chromacomponents in the YUV 4:4:4 format.

In another example, a device for processing video data includes: amemory configured to store video data; and one or more processorsimplemented in circuitry and configured to: obtain unfiltered referencesamples for an area of a picture of the video data, wherein the one ormore processors are configured to disable intra-reference samplesmoothing of the unfiltered reference samples for chroma samples in aYUV 4:2:0 format and in a YUV 4:4:4 format; and generate, usingintra-prediction, chroma samples of a predicted block for a block of thepicture based on the unfiltered reference samples when generating thechroma components in the YUV 4:2:0 format and when generating the chromacomponents in the YUV 4:4:4 format.

In one example, a computer-readable storage medium includes storedthereon instructions that, when executed, cause one or more processorsto: obtain unfiltered reference samples for an area of a picture of thevideo data, wherein the instructions further cause the one or moreprocessors to disable intra-reference sample smoothing of the unfilteredreference samples for chroma samples in a YUV 4:2:0 format and in a YUV4:4:4 format; and generate, using intra-prediction, chroma samples of apredicted block for a block of the picture based on the unfilteredreference samples when generating the chroma components in the YUV 4:2:0format and when generating the chroma components in the YUV 4:4:4format.

In another example, a device for coding video data includes: means forobtaining unfiltered reference samples for an area of a picture; andmeans for generating, using intra-prediction, chroma samples of apredicted block for a block of the picture based on the unfilteredreference samples when generating the chroma components in a YUV 4:2:0format and when generating the chroma components in a YUV 4:4:4 format.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may perform the techniques of this disclosure.

FIGS. 2A and 2B are conceptual diagrams illustrating an example quadtreebinary tree (QTBT) structure, and a corresponding coding tree unit(CTU).

FIG. 3 is a block diagram illustrating an example video encoder that mayperform the techniques of this disclosure.

FIG. 4 is a block diagram illustrating an example video decoder that mayperform the techniques of this disclosure.

FIG. 5A is a conceptual diagram illustrating a first example ofsplitting a coding unit into a first triangle-shaped partition and asecond triangle-shaped partition based on inter prediction, inaccordance with the techniques of the disclosure.

FIG. 5B is a conceptual diagram illustrating a second example ofsplitting a coding unit into a first triangle-shaped partition and asecond triangle-shaped partition based on inter prediction, inaccordance with the techniques of the disclosure.

FIG. 6 is a conceptual diagram illustrating pixel blending with one setof weights, in accordance with the techniques of the disclosure.

FIG. 7A is a conceptual diagram illustrating further details of a firsttriangle-shaped partition for the pixel blending of FIG. 6, inaccordance with the techniques of the disclosure.

FIG. 7B is a conceptual diagram illustrating further details of a secondtriangle-shaped partition for the pixel blending of FIG. 6, inaccordance with the techniques of the disclosure.

FIG. 7C is a conceptual diagram illustrating further details of a blockformed using the pixel blending of FIG. 6, in accordance with thetechniques of the disclosure.

FIG. 8 is a flowchart illustrating an example method for encoding acurrent block, in accordance with the techniques of the disclosure.

FIG. 9 is a flowchart illustrating an example method for decoding acurrent block of video data, in accordance with the techniques of thedisclosure.

FIG. 10 is a flowchart illustrating an example process for pixelblending of chroma components for a block of video data with a set ofweights for a YUV 4:2:0 sampling format, in accordance with thetechniques of the disclosure.

FIG. 11 is a flowchart illustrating an example process for generatingchroma samples of a prediction block using intra-prediction.

DETAILED DESCRIPTION

As described in more detail below, the disclosure describes exampletechniques for improving an encoding and/or decoding of chromacomponents in different formats. For example, when using triangularprediction unit (PU) mode, a video coder (e.g., a video encoder or videodecoder) may split a PU into two triangle-shaped partitions. In thisexample, the video coder may generate motion compensated triangle-shapedpartitions and combine the motion compensated triangle-shaped partitionsusing a set of weights that are based on the chroma format. For example,the video coder may apply pixel blending using a first set of weightswhen chroma components are in a YUV 4:4:4 format and apply a second setof weights, different from the first set of weights, when chromacomponents are in a YUV 4:2:0 format. However, using different sets ofweights for different chroma formats may increase a complexity ofgenerating the chroma components.

In accordance with the techniques of the disclosure, a video coder(e.g., a video encoder or video decoder) may be configured to unify atreatment of chroma components for different chroma formats. Forexample, the video coder may apply pixel blending using a set of weightsfor a YUV 4:2:0 format when chroma components are in a YUV 4:4:4 formatand apply the set of weights for the YUV 4:2:0 format when chromacomponents are in the YUV 4:2:0 format.

In some examples, a video coder (e.g., a video encoder or a videodecoder) may be configured to generate chroma samples of a predictionblock for a block of video data using unfiltered reference samples whenintra-prediction is used and when chroma components are in a YUV 4:2:0format. In this example, the video coder may be configured to generatechroma samples of a prediction block for a block of video data usingfiltered reference samples when intra-prediction is used and when chromacomponents are in a YUV 4:4:4 format. However, using different referencesamples for different chroma formats may increase a complexity ofgenerating the chroma components.

In accordance with the techniques of the disclosure, a video coder(e.g., a video encoder or video decoder) may be configured to unify atreatment of chroma components for different chroma formats. Forexample, the video coder may be configured to disable intra referencesample smoothing when chroma components are in a YUV 4:2:0 format andwhen chroma components are in a YUV 4:4:4 format. For example, the videocoder may generate chroma samples of a prediction block for a block ofvideo data using unfiltered reference samples when chroma components arein a YUV 4:2:0 format and when chroma components are in a YUV 4:4:4format.

Techniques described herein for unifying a treatment of chromacomponents may be applied to any of the existing video codecs, such asHEVC (High Efficiency Video Coding), or video codecs under developmentsuch as VVC (Versatile Video Coding), or be an efficient coding tool inany future video coding standards. While examples of describestechniques related to weighted prediction are described with relation toHEVC and on-going works in Versatile Video Coding (VVC), techniquesdescribed herein may be applied to other existing video codecs and/orfuture video coding standards.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system 100 that may perform the techniques of this disclosure.The techniques of this disclosure are generally directed to coding(encoding and/or decoding) video data. In general, video data includesany data for processing a video. Thus, video data may include raw,uncoded video, encoded video, decoded (e.g., reconstructed) video, andvideo metadata, such as signaling data.

As shown in FIG. 1, system 100 includes a source device 102 thatprovides encoded video data to be decoded and displayed by a destinationdevice 116, in this example. In particular, source device 102 providesthe video data to destination device 116 via a computer-readable medium110. Source device 102 and destination device 116 may comprise any of awide range of devices, including desktop computers, notebook (i.e.,laptop) computers, tablet computers, set-top boxes, telephone handsetssuch smartphones, televisions, cameras, display devices, digital mediaplayers, video gaming consoles, video streaming device, or the like. Insome cases, source device 102 and destination device 116 may be equippedfor wireless communication, and thus may be referred to as wirelesscommunication devices.

In the example of FIG. 1, source device 102 includes video source 104,memory 106, video encoder 200, and output interface 108. Destinationdevice 116 includes input interface 122, video decoder 300, memory 120,and display device 118. In accordance with this disclosure, videoencoder 200 of source device 102 and video decoder 300 of destinationdevice 116 may be configured to apply the techniques for unifying weightinformation for different chroma formats. Thus, source device 102represents an example of a video encoding device, while destinationdevice 116 represents an example of a video decoding device. In otherexamples, a source device and a destination device may include othercomponents or arrangements. For example, source device 102 may receivevideo data from an external video source, such as an external camera.Likewise, destination device 116 may interface with an external displaydevice, rather than including an integrated display device.

System 100 as shown in FIG. 1 is merely one example. In general, anydigital video encoding and/or decoding device may perform techniques fordetermining weight information for a first chroma format, determiningweight information for a second chroma format different from the firstchroma format to correspond to the weight information for the firstchroma format, and generating prediction information based on the weightinformation for the first chroma format. Source device 102 anddestination device 116 are merely examples of such coding devices inwhich source device 102 generates coded video data for transmission todestination device 116. This disclosure refers to a “coding” device as adevice that performs coding (encoding and/or decoding) of data. Thus,video encoder 200 and video decoder 300 represent examples of codingdevices, in particular, a video encoder and a video decoder,respectively. In some examples, devices 102, 116 may operate in asubstantially symmetrical manner such that each of devices 102, 116include video encoding and decoding components. Hence, system 100 maysupport one-way or two-way video transmission between video devices 102,116, e.g., for video streaming, video playback, video broadcasting, orvideo telephony.

In general, video source 104 represents a source of video data (i.e.,raw, uncoded video data) and provides a sequential series of pictures(also referred to as “frames”) of the video data to video encoder 200,which encodes data for the pictures. Video source 104 of source device102 may include a video capture device, such as a video camera, a videoarchive containing previously captured raw video, and/or a video feedinterface to receive video from a video content provider. As a furtheralternative, video source 104 may generate computer graphics-based dataas the source video, or a combination of live video, archived video, andcomputer-generated video. In each case, video encoder 200 encodes thecaptured, pre-captured, or computer-generated video data. Video encoder200 may rearrange the pictures from the received order (sometimesreferred to as “display order”) into a coding order for coding. Videoencoder 200 may generate a bitstream including encoded video data.Source device 102 may then output the encoded video data via outputinterface 108 onto computer-readable medium 110 for reception and/orretrieval by, e.g., input interface 122 of destination device 116.

Memory 106 of source device 102 and memory 120 of destination device 116represent general purpose memories. In some example, memories 106, 120may store raw video data, e.g., raw video from video source 104 and raw,decoded video data from video decoder 300. Additionally, oralternatively, memories 106, 120 may store software instructionsexecutable by, e.g., video encoder 200 and video decoder 300,respectively. Although shown separately from video encoder 200 and videodecoder 300 in this example, it should be understood that video encoder200 and video decoder 300 may also include internal memories forfunctionally similar or equivalent purposes. Furthermore, memories 106,120 may store encoded video data, e.g., output from video encoder 200and input to video decoder 300. In some examples, portions of memories106, 120 may be allocated as one or more video buffers, e.g., to storeraw, decoded, and/or encoded video data.

Computer-readable medium 110 may represent any type of medium or devicecapable of transporting the encoded video data from source device 102 todestination device 116. In one example, computer-readable medium 110represents a communication medium to enable source device 102 totransmit encoded video data directly to destination device 116 inreal-time, e.g., via a radio frequency network or computer-basednetwork. Output interface 108 may modulate a transmission signalincluding the encoded video data, and input interface 122 may modulatethe received transmission signal, according to a communication standard,such as a wireless communication protocol. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device 102 to destination device 116.

In some examples, source device 102 may output encoded data from outputinterface 108 to storage device 116. Similarly, destination device 116may access encoded data from storage device 116 via input interface 122.Storage device 116 may include any of a variety of distributed orlocally accessed data storage media such as a hard drive, Blu-ray discs,DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or anyother suitable digital storage media for storing encoded video data.

In some examples, source device 102 may output encoded video data tofile server 114 or another intermediate storage device that may storethe encoded video generated by source device 102. Destination device 116may access stored video data from file server 114 via streaming ordownload. File server 114 may be any type of server device capable ofstoring encoded video data and transmitting that encoded video data tothe destination device 116. File server 114 may represent a web server(e.g., for a website), a File Transfer Protocol (FTP) server, a contentdelivery network device, or a network attached storage (NAS) device.Destination device 116 may access encoded video data from file server114 through any standard data connection, including an Internetconnection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., DSL, cable modem, etc.), or acombination of both that is suitable for accessing encoded video datastored on file server 114. File server 114 and input interface 122 maybe configured to operate according to a streaming transmission protocol,a download transmission protocol, or a combination thereof.

Output interface 108 and input interface 122 may represent wirelesstransmitters/receiver, modems, wired networking components (e.g.,Ethernet cards), wireless communication components that operateaccording to any of a variety of IEEE 802.11 standards, or otherphysical components. In examples where output interface 108 and inputinterface 122 comprise wireless components, output interface 108 andinput interface 122 may be configured to transfer data, such as encodedvideo data, according to a cellular communication standard, such as 4G,4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In someexamples where output interface 108 comprises a wireless transmitter,output interface 108 and input interface 122 may be configured totransfer data, such as encoded video data, according to other wirelessstandards, such as an IEEE 802.11 specification, an IEEE 802.15specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. Insome examples, source device 102 and/or destination device 116 mayinclude respective system-on-a-chip (SoC) devices. For example, sourcedevice 102 may include an SoC device to perform the functionalityattributed to video encoder 200 and/or output interface 108, anddestination device 116 may include an SoC device to perform thefunctionality attributed to video decoder 300 and/or input interface122.

The techniques of this disclosure may be applied to video coding insupport of any of a variety of multimedia applications, such asover-the-air television broadcasts, cable television transmissions,satellite television transmissions, Internet streaming videotransmissions, such as dynamic adaptive streaming over HTTP (DASH),digital video that is encoded onto a data storage medium, decoding ofdigital video stored on a data storage medium, or other applications.

Input interface 122 of destination device 116 receives an encoded videobitstream from computer-readable medium 110 (e.g., storage device 112,file server 114, or the like). The encoded video bitstream fromcomputer-readable medium 110 may include signaling information definedby video encoder 200, which is also used by video decoder 300, such assyntax elements having values that describe characteristics and/orprocessing of video blocks or other coded units (e.g., slices, pictures,groups of pictures, sequences, or the like). Display device 118 displaysdecoded pictures of the decoded video data to a user. Display device 118may represent any of a variety of display devices such as a cathode raytube (CRT), a liquid crystal display (LCD), a plasma display, an organiclight emitting diode (OLED) display, or another type of display device.

Although not shown in FIG. 1, in some examples, video encoder 200 andvideo decoder 300 may each be integrated with an audio encoder and/oraudio decoder, and may include appropriate MUX-DEMUX units, or otherhardware and/or software, to handle multiplexed streams including bothaudio and video in a common data stream. If applicable, MUX-DEMUX unitsmay conform to the ITU H.223 multiplexer protocol, or other protocolssuch as the user datagram protocol (UDP).

Video encoder 200 and video decoder 300 each may be implemented as anyof a variety of suitable encoder and/or decoder circuitry, such as oneor more microprocessors, digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), discrete logic, software, hardware, firmware or anycombinations thereof. When the techniques are implemented partially insoftware, a device may store instructions for the software in asuitable, non-transitory computer-readable medium and execute theinstructions in hardware using one or more processors to perform thetechniques of this disclosure. Each of video encoder 200 and videodecoder 300 may be included in one or more encoders or decoders, eitherof which may be integrated as part of a combined encoder/decoder (CODEC)in a respective device. A device including video encoder 200 and/orvideo decoder 300 may comprise an integrated circuit, a microprocessor,and/or a wireless communication device, such as a cellular telephone.

Video encoder 200 and video decoder 300 may operate according to a videocoding standard, such as ITU-T H.265, also referred to as HighEfficiency Video Coding (HEVC) or extensions thereto, such as themulti-view and/or scalable video coding extensions. Alternatively, videoencoder 200 and video decoder 300 may operate according to otherproprietary or industry standards, such as the Joint Exploration TestModel (JEM) or ITU-T H.266, also referred to as Versatile Video Coding(VVC). A recent draft of the VVC standard is described in Bross, et al.“Versatile Video Coding (Draft 7),” Joint Video Experts Team (WET) ofITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 16^(th) Meeting: Geneva,CH, 1-11 Oct. 2019, JVET-P2001-v9 (hereinafter “VVC Draft 7”). Thetechniques of this disclosure, however, are not limited to anyparticular coding standard.

In general, video encoder 200 and video decoder 300 may performblock-based coding of pictures. The term “block” generally refers to astructure including data to be processed (e.g., encoded, decoded, orotherwise used in the encoding and/or decoding process). For example, ablock may include a two-dimensional matrix of samples of luminanceand/or chrominance data. In general, video encoder 200 and video decoder300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format.That is, rather than coding red, green, and blue (RGB) data for samplesof a picture, video encoder 200 and video decoder 300 may code luminanceand chrominance components, where the chrominance components may includeboth red hue and blue hue chrominance components. In some examples,video encoder 200 converts received RGB formatted data to a YUVrepresentation prior to encoding, and video decoder 300 converts the YUVrepresentation to the RGB format. Alternatively, pre-processing unitsand post-processing units (not shown) may perform these conversions.

YUV 4:4:4 may refer to a YUV representation where each of the threecomponents (e.g., Y, Cb, Cr) has a same sampling rate and no chromasubsampling. For example, a luma (e.g., Y) component of YUV 4:4:4 mayhave a first resolution. In this example, a first chroma component(e.g., Cb) component of YUV 4:4:4 may have the first resolution of theluma component and a second chroma component (e.g., Cr) component of YUV4:4:4 may have the first resolution of the luma component. In contrast,YUV 4:2:0 may refer to a YUV representation where each of the chromacomponents (e.g., Cb, Cr) has half a sampling rate of a luma componentin both a vertical and horizontal direction and therefore YUV 4:2:0 mayhave chroma subsampling. For example, a luma (e.g., Y) component of YUV4:4:4 may have a first resolution. In this example, a first chromacomponent (e.g., Cb) component of YUV 4:4:4 may have a second resolution(e.g., vertical and horizontal) that is half of the first resolution ofthe luma component and a second chroma component (e.g., Cr) component ofYUV 4:4:4 may have a second resolution (e.g., vertical and horizontal)that is half of the first resolution of the luma component, and the sameas the second resolution of the first chroma component. While thisdisclosure refers to YUV 4:4:4 and YUV 4:2:0 as examples of chromaformats, other examples may use other formats (e.g., YUV 4:2:2, etc.).

This disclosure may generally refer to coding (e.g., encoding anddecoding) of pictures to include the process of encoding or decodingdata of the picture. Similarly, this disclosure may refer to coding ofblocks of a picture to include the process of encoding or decoding datafor the blocks, e.g., prediction and/or residual coding. An encodedvideo bitstream generally includes a series of values for syntaxelements representative of coding decisions (e.g., coding modes) andpartitioning of pictures into blocks. Thus, references to coding apicture or a block should generally be understood as coding values forsyntax elements forming the picture or block.

HEVC defines various blocks, including coding units (CUs), predictionunits (PUs), and transform units (TUs). According to HEVC, a video coder(such as video encoder 200) partitions a coding tree unit (CTU) into CUsaccording to a quadtree structure. That is, the video coder partitionsCTUs and CUs into four equal, non-overlapping squares, and each node ofthe quadtree has either zero or four child nodes. Nodes without childnodes may be referred to as “leaf nodes,” and CUs of such leaf nodes mayinclude one or more PUs and/or one or more TUs. The video coder mayfurther partition PUs and TUs. For example, in HEVC, a residual quadtree(RQT) represents partitioning of TUs. In HEVC, PUs representinter-prediction data, while TUs represent residual data. CUs that areintra-predicted include intra-prediction information, such as anintra-mode indication.

As another example, video encoder 200 and video decoder 300 may beconfigured to operate according to JEM or VVC. According to JEM or VVC,a video coder (such as video encoder 200) partitions a picture into aplurality of coding tree units (CTUs). Video encoder 200 may partition aCTU according to a tree structure, such as a quadtree-binary tree (QTBT)structure or Multi-Type Tree (MTT) structure. The QTBT structure removesthe concepts of multiple partition types, such as the separation betweenCUs, PUs, and TUs of HEVC. A QTBT structure includes two levels: a firstlevel partitioned according to quadtree partitioning, and a second levelpartitioned according to binary tree partitioning. A root node of theQTBT structure corresponds to a CTU. Leaf nodes of the binary treescorrespond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using aquadtree (QT) partition, a binary tree (BT) partition, and one or moretypes of triple tree (TT) partitions. A triple tree partition is apartition where a block is split into three sub-blocks. In someexamples, a triple tree partition divides a block into three sub-blockswithout dividing the original block through the center. The partitioningtypes in MTT (e.g., QT, BT, and TT), may be symmetrical or asymmetrical.

In some examples, video encoder 200 and video decoder 300 may use asingle QTBT or MTT structure to represent each of the luminance andchrominance components, while in other examples, video encoder 200 andvideo decoder 300 may use two or more QTBT or MTT structures, such asone QTBT/MTT structure for the luminance component and another QTBT/MTTstructure for both chrominance components (or two QTBT/MTT structuresfor respective chrominance components).

Video encoder 200 and video decoder 300 may be configured to usequadtree partitioning per HEVC, QTBT partitioning, MTT partitioning, orother partitioning structures. For purposes of explanation, thedescription of the techniques of this disclosure is presented withrespect to QTBT partitioning. However, it should be understood that thetechniques of this disclosure may also be applied to video codersconfigured to use quadtree partitioning, or other types of partitioningas well.

This disclosure may use “N×N” and “N by N” interchangeably to refer tothe sample dimensions of a block (such as a CU or other video block) interms of vertical and horizontal dimensions, e.g., 16×16 samples or 16by 16 samples. In general, a 16×16 CU will have 16 samples in a verticaldirection (y=16) and 16 samples in a horizontal direction (x=16).Likewise, an N×N CU generally has N samples in a vertical direction andN samples in a horizontal direction, where N represents a nonnegativeinteger value. The samples in a CU may be arranged in rows and columns.Moreover, CUs need not necessarily have the same number of samples inthe horizontal direction as in the vertical direction. For example, CUsmay comprise N×M samples, where M is not necessarily equal to N.

Video encoder 200 encodes video data for CUs representing predictionand/or residual information, and other information. The predictioninformation indicates how the CU is to be predicted in order to form aprediction block for the CU. The residual information generallyrepresents sample-by-sample differences between samples of the CU priorto encoding and the prediction block.

To predict a CU, video encoder 200 may generally form a prediction blockfor the CU through inter-prediction or intra-prediction.Inter-prediction generally refers to predicting the CU from data of apreviously coded picture, whereas intra-prediction generally refers topredicting the CU from previously coded data of the same picture. Toperform inter-prediction, video encoder 200 may generate the predictionblock using one or more motion vectors. Video encoder 200 may generallyperform a motion search to identify a reference block that closelymatches the CU, e.g., in terms of differences between the CU and thereference block. Video encoder 200 may calculate a difference metricusing a sum of absolute difference (SAD), sum of squared differences(SSD), mean absolute difference (MAD), mean squared differences (MSD),or other such difference calculations to determine whether a referenceblock closely matches the current CU. In some examples, video encoder200 may predict the current CU using uni-directional prediction orbi-directional prediction.

Some examples of JEM and VVC also provide an affine motion compensationmode, which may be considered an inter-prediction mode. In affine motioncompensation mode, video encoder 200 may determine two or more motionvectors that represent non-translational motion, such as zoom in or out,rotation, perspective motion, or other irregular motion types.

To perform intra-prediction, video encoder 200 may select anintra-prediction mode to generate the prediction block. Some examples ofJEM and VVC provide sixty-seven intra-prediction modes, includingvarious directional modes, as well as planar mode and DC mode. Ingeneral, video encoder 200 selects an intra-prediction mode thatdescribes neighboring samples to a current block (e.g., a block of a CU)from which to predict samples of the current block. Such samples maygenerally be above, above and to the left, or to the left of the currentblock in the same picture as the current block, assuming video encoder200 codes CTUs and CUs in raster scan order (left to right, top tobottom).

Video encoder 200 encodes data representing the prediction mode for acurrent block. For example, for inter-prediction modes, video encoder200 may encode data representing which of the various availableinter-prediction modes is used, as well as motion information for thecorresponding mode. For uni-directional or bi-directionalinter-prediction, for example, video encoder 200 may encode motionvectors using advanced motion vector prediction (AMVP) or merge mode.Video encoder 200 may use similar modes to encode motion vectors foraffine motion compensation mode.

Following prediction, such as intra-prediction or inter-prediction of ablock, video encoder 200 may calculate residual data for the block. Theresidual data, such as a residual block, represents sample by sampledifferences between the block and a prediction block for the block,formed using the corresponding prediction mode. Video encoder 200 mayapply one or more transforms to the residual block, to producetransformed data in a transform domain instead of the sample domain. Forexample, video encoder 200 may apply a discrete cosine transform (DCT),an integer transform, a wavelet transform, or a conceptually similartransform to residual video data. Additionally, video encoder 200 mayapply a secondary transform following the first transform, such as amode-dependent non-separable secondary transform (MDNSST), a signaldependent transform, a Karhunen-Loeve transform (KLT), or the like.Video encoder 200 produces transform coefficients following applicationof the one or more transforms.

As noted above, following any transforms to produce transformcoefficients, video encoder 200 may perform quantization of thetransform coefficients. Quantization generally refers to a process inwhich transform coefficients are quantized to possibly reduce the amountof data used to represent the coefficients, providing furthercompression. By performing the quantization process, video encoder 200may reduce the bit depth associated with some or all of thecoefficients. For example, video encoder 200 may round an n-bit valuedown to an m-bit value during quantization, where n is greater than m.In some examples, to perform quantization, video encoder 200 may performa bitwise right-shift of the value to be quantized.

Following quantization, video encoder 200 may scan the transformcoefficients, producing a one-dimensional vector from thetwo-dimensional matrix including the quantized transform coefficients.The scan may be designed to place higher energy (and therefore lowerfrequency) coefficients at the front of the vector and to place lowerenergy (and therefore higher frequency) transform coefficients at theback of the vector. In some examples, video encoder 200 may utilize apredefined scan order to scan the quantized transform coefficients toproduce a serialized vector, and then entropy encode the quantizedtransform coefficients of the vector. In other examples, video encoder200 may perform an adaptive scan. After scanning the quantized transformcoefficients to form the one-dimensional vector, video encoder 200 mayentropy encode the one-dimensional vector, e.g., according tocontext-adaptive binary arithmetic coding (CABAC). Video encoder 200 mayalso entropy encode values for syntax elements describing metadataassociated with the encoded video data for use by video decoder 300 indecoding the video data.

To perform CABAC, video encoder 200 may assign a context within acontext model to a symbol to be transmitted. The context may relate to,for example, whether neighboring values of the symbol are zero-valued ornot. The probability determination may be based on a context assigned tothe symbol.

Video encoder 200 may further generate syntax data, such as block-basedsyntax data, picture-based syntax data, and sequence-based syntax data,to video decoder 300, e.g., in a picture header, a block header, a sliceheader, or other syntax data, such as a sequence parameter set (SPS),picture parameter set (PPS), or video parameter set (VPS). Video decoder300 may likewise decode such syntax data to determine how to decodecorresponding video data.

In this manner, video encoder 200 may generate a bitstream includingencoded video data, e.g., syntax elements describing partitioning of apicture into blocks (e.g., CUs) and prediction and/or residualinformation for the blocks. Ultimately, video decoder 300 may receivethe bitstream and decode the encoded video data.

In general, video decoder 300 performs a reciprocal process to thatperformed by video encoder 200 to decode the encoded video data of thebitstream. For example, video decoder 300 may decode values for syntaxelements of the bitstream using CABAC in a manner substantially similarto, albeit reciprocal to, the CABAC encoding process of video encoder200. The syntax elements may define partitioning information of apicture into CTUs, and partitioning of each CTU according to acorresponding partition structure, such as a QTBT structure, to defineCUs of the CTU. The syntax elements may further define prediction andresidual information for blocks (e.g., CUs) of video data.

The residual information may be represented by, for example, quantizedtransform coefficients. Video decoder 300 may inverse quantize andinverse transform the quantized transform coefficients of a block toreproduce a residual block for the block. Video decoder 300 uses asignaled prediction mode (intra- or inter-prediction) and relatedprediction information (e.g., motion information for inter-prediction)to form a prediction block for the block. Video decoder 300 may thencombine the prediction block and the residual block (on asample-by-sample basis) to reproduce the original block. That is, forexample, video decoder 300 may combine the predicted block and theresidual block to decode an unfiltered reconstructed block for the blockof video data. In some examples, video decoder 300 may store theunfiltered reconstructed block at DPB 314. Video decoder 300 may performadditional processing, such as performing a deblocking process to reducevisual artifacts along boundaries of the block. That is, for example,video decoder 300 may generate a filtered reconstructed block for theblock of video data, where generating the filtered reconstructed blockcomprises performing one or more filter operations on the unfilteredreconstructed block. In this example, video decoder 300 may store thefiltered reconstructed block at DPB 314.

In accordance with the techniques of this disclosure, video encoder 200and/or video decoder 300 may be configured to generate a coding unit fora chroma component of a block of video data in a YUV 4:4:4 format or ina YUV 4:2:0 format. In this example, video encoder 200 or video decoder300 may be configured to split the coding unit for the chroma componentinto a first triangle-shaped partition and a second triangle-shapedpartition based on enabling of a triangular prediction unit mode. Videoencoder 200 or video decoder 300 may be configured to apply pixelblending using a set of weights for the YUV 4:2:0 format to generate apredicted block for the chroma component when the one or more processorsgenerate the coding unit for the chroma component in the YUV 4:2:0format and when the one or more processors generate the coding unit forthe chroma component in the YUV 4:4:4 format. Using a single set ofweights for generating coding unit for a chroma component in the YUV4:2:0 format and in the YUV 4:4:4 format may reduce a complexity ofdecoding video data, which may reduce an amount of time video encoder200 and video decoder 300 decode video data and/or reduce a powerconsumption of video encoder 200 and video decoder 300.

To apply pixel blending, video encoder 200 or video decoder 300 may beconfigured to determine weighted averages, using the set of weights forthe YUV 4:2:0 format, of collocated motion compensated pixels of thefirst triangle-shaped partition and the second triangle-shaped partitionbased on motion information of the first triangle-shaped partition andthe second triangle-shaped partition, respectively.

In some examples, video encoder 200 and/or video decoder 300 may beconfigured to obtain unfiltered reference samples for an area of apicture. In this example, video encoder 200 and/or video decoder 300 maybe configured to disable intra-reference sample smoothing of theunfiltered reference samples for chroma samples in a YUV 4:2:0 formatand in a YUV 4:4:4 format. Video encoder 200 and/or video decoder 300may be configured to generate, using intra-prediction, chroma samples ofa prediction block for a block of the picture based on the unfilteredreference samples when generating the chroma components in the YUV 4:2:0format and when generating the chroma components in the YUV 4:4:4format. Disabling intra-reference sample smoothing of the unfilteredreference samples for chroma samples in a YUV 4:2:0 format and in a YUV4:4:4 format may reduce a complexity of decoding video data, which mayreduce an amount of time video encoder 200 and video decoder 300 decodevideo data and/or reduce a power consumption of video encoder 200 andvideo decoder 300.

This disclosure may generally refer to “signaling” certain information,such as syntax elements. The term “signaling” may generally refer to thecommunication of values syntax elements and/or other data used to decodeencoded video data. That is, video encoder 200 may signal values forsyntax elements in the bitstream. In general, signaling refers togenerating a value in the bitstream. As noted above, source device 102may transport the bitstream to destination device 116 substantially inreal time, or not in real time, such as might occur when storing syntaxelements to storage device 112 for later retrieval by destination device116.

FIGS. 2A and 2B are conceptual diagram illustrating an example quadtreebinary tree (QTBT) structure 130, and a corresponding coding tree unit(CTU) 132. The solid lines represent quadtree splitting, and dottedlines indicate binary tree splitting. In each split (i.e., non-leaf)node of the binary tree, one flag is signaled to indicate whichsplitting type (i.e., horizontal or vertical) is used, where 0 indicateshorizontal splitting and 1 indicates vertical splitting in this example.For the quadtree splitting, there is no need to indicate the splittingtype, since quadtree nodes split a block horizontally and verticallyinto 4 sub-blocks with equal size. Accordingly, video encoder 200 mayencode, and video decoder 300 may decode, syntax elements (such assplitting information) for a region tree level of QTBT structure 130(i.e., the solid lines) and syntax elements (such as splittinginformation) for a prediction tree level of QTBT structure 130 (i.e.,the dashed lines). Video encoder 200 may encode, and video decoder 300may decode, video data, such as prediction and transform data, for CUsrepresented by terminal leaf nodes of QTBT structure 130.

In general, CTU 132 of FIG. 2B may be associated with parametersdefining sizes of blocks corresponding to nodes of QTBT structure 130 atthe first and second levels. These parameters may include a CTU size(representing a size of CTU 132 in samples), a minimum quadtree size(MinQTSize, representing a minimum allowed quadtree leaf node size), amaximum binary tree size (MaxBTSize, representing a maximum allowedbinary tree root node size), a maximum binary tree depth (MaxBTDepth,representing a maximum allowed binary tree depth), and a minimum binarytree size (MinBTSize, representing the minimum allowed binary tree leafnode size).

The root node of a QTBT structure corresponding to a CTU may have fourchild nodes at the first level of the QTBT structure, each of which maybe partitioned according to quadtree partitioning. That is, nodes of thefirst level are either leaf nodes (having no child nodes) or have fourchild nodes. The example of QTBT structure 130 represents such nodes asincluding the parent node and child nodes having solid lines forbranches. If nodes of the first level are not larger than the maximumallowed binary tree root node size (MaxBTSize), they can be furtherpartitioned by respective binary trees. The binary tree splitting of onenode can be iterated until the nodes resulting from the split reach theminimum allowed binary tree leaf node size (MinBTSize) or the maximumallowed binary tree depth (MaxBTDepth). The example of QTBT structure130 represents such nodes as having dashed lines for branches. Thebinary tree leaf node is referred to as a coding unit (CU), which isused for prediction (e.g., intra-picture or inter-picture prediction)and transform, without any further partitioning. As discussed above, CUsmay also be referred to as “video blocks” or “blocks.”

In one example of the QTBT partitioning structure, the CTU size is setas 128×128 (luma samples and two corresponding 64×64 chroma samples),the MinQTSize is set as 16×16, the MaxBTSize is set as 64×64, theMinBTSize (for both width and height) is set as 4, and the MaxBTDepth isset as 4. The quadtree partitioning is applied to the CTU first togenerate quad-tree leaf nodes. The quadtree leaf nodes may have a sizefrom 16×16 (i.e., the MinQTSize) to 128×128 (i.e., the CTU size). If theleaf quadtree node is 128×128, it will not be further split by thebinary tree, since the size exceeds the MaxBTSize (i.e., 64×64, in thisexample). Otherwise, the leaf quadtree node will be further partitionedby the binary tree. Therefore, the quadtree leaf node is also the rootnode for the binary tree and has the binary tree depth as 0. When thebinary tree depth reaches MaxBTDepth (4, in this example), no furthersplitting is permitted. When the binary tree node has width equal toMinBTSize (4, in this example), it implies no further horizontalsplitting is permitted. Similarly, a binary tree node having a heightequal to MinBTSize implies no further vertical splitting is permittedfor that binary tree node. As noted above, leaf nodes of the binary treeare referred to as CUs and are further processed according to predictionand transform without further partitioning.

FIG. 3 is a block diagram illustrating an example video encoder 200 thatmay perform the techniques of this disclosure. FIG. 3 is provided forpurposes of explanation and should not be considered limiting of thetechniques as broadly exemplified and described in this disclosure. Forpurposes of explanation, this disclosure describes video encoder 200 inthe context of video coding standards such as the HEVC video codingstandard and the JEM, VVC (ITU-T H.266) video coding standard indevelopment. However, the techniques of this disclosure are not limitedto these video coding standards, and are applicable generally to videoencoding and decoding.

In the example of FIG. 3, video encoder 200 includes video data memory230, mode selection unit 202, residual generation unit 204, transformprocessing unit 206, quantization unit 208, inverse quantization unit210, inverse transform processing unit 212, reconstruction unit 214,filter unit 216, decoded picture buffer (DPB) 218, and entropy encodingunit 220. Any or all of video data memory 230, mode selection unit 202,residual generation unit 204, transform processing unit 206,quantization unit 208, inverse quantization unit 210, inverse transformprocessing unit 212, reconstruction unit 214, filter unit 216, DPB 218,and entropy encoding unit 220 may be implemented in one or moreprocessors or in processing circuitry. For instance, the units of videoencoder 200 may be implemented as one or more circuits or logic elementsforming part of a processor, ASIC, or FPGA. Moreover, video encoder 200may include additional or alternative processors or processing circuitryto perform these and other functions.

Video data memory 230 may store video data to be encoded by thecomponents of video encoder 200. Video encoder 200 may receive the videodata stored in video data memory 230 from, for example, video source 104(FIG. 1). DPB 218 may act as a reference picture memory that storesreference video data for use in prediction of subsequent video data byvideo encoder 200. Video data memory 230 and DPB 218 may be formed byany of a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. Video datamemory 230 and DPB 218 may be provided by the same memory device orseparate memory devices. In various examples, video data memory 230 maybe on-chip with other components of video encoder 200, as illustrated,or off-chip relative to those components.

In this disclosure, reference to video data memory 230 should not beinterpreted as being limited to memory internal to video encoder 200,unless specifically described as such, or memory external to videoencoder 200, unless specifically described as such. Rather, reference tovideo data memory 230 should be understood as reference memory thatstores video data that video encoder 200 receives for encoding (e.g.,video data for a current block that is to be encoded). Memory 106 ofFIG. 1 may also provide temporary storage of outputs from the variousunits of video encoder 200.

The various units of FIG. 3 are illustrated to assist with understandingthe operations performed by video encoder 200. The units may beimplemented as fixed-function circuits, programmable circuits, or acombination thereof. Fixed-function circuits refer to circuits thatprovide particular functionality, and are preset on the operations thatcan be performed. Programmable circuits refer to circuits that canprogrammed to perform various tasks, and provide flexible functionalityin the operations that can be performed. For instance, programmablecircuits may execute software or firmware that cause the programmablecircuits to operate in the manner defined by instructions of thesoftware or firmware. Fixed-function circuits may execute softwareinstructions (e.g., to receive parameters or output parameters), but thetypes of operations that the fixed-function circuits perform aregenerally immutable. In some examples, the one or more of the units maybe distinct circuit blocks (fixed-function or programmable), and in someexamples, the one or more units may be integrated circuits.

Video encoder 200 may include arithmetic logic units (ALUs), elementaryfunction units (EFUs), digital circuits, analog circuits, and/orprogrammable cores, formed from programmable circuits. In examples wherethe operations of video encoder 200 are performed using softwareexecuted by the programmable circuits, memory 106 (FIG. 1) may store theobject code of the software that video encoder 200 receives andexecutes, or another memory within video encoder 200 (not shown) maystore such instructions.

Video data memory 230 is configured to store received video data. Videoencoder 200 may retrieve a picture of the video data from video datamemory 230 and provide the video data to residual generation unit 204and mode selection unit 202. Video data in video data memory 230 may beraw video data that is to be encoded.

Mode selection unit 202 includes a motion estimation unit 222, motioncompensation unit 224, and an intra-prediction unit 226. Mode selectionunit 202 may include additional functional units to perform videoprediction in accordance with other prediction modes. As examples, modeselection unit 202 may include a palette unit, an intra-block copy unit(which may be part of motion estimation unit 222 and/or motioncompensation unit 224), an affine unit, a linear model (LM) unit, or thelike.

Mode selection unit 202 generally coordinates multiple encoding passesto test combinations of encoding parameters and resultingrate-distortion values for such combinations. The encoding parametersmay include partitioning of CTUs into CUs, prediction modes for the CUs,transform types for residual data of the CUs, quantization parametersfor residual data of the CUs, and so on. Mode selection unit 202 mayultimately select the combination of encoding parameters havingrate-distortion values that are better than the other testedcombinations.

Video encoder 200 may partition a picture retrieved from video datamemory 230 into a series of CTUs, and encapsulate one or more CTUswithin a slice. Mode selection unit 202 may partition a CTU of thepicture in accordance with a tree structure, such as the QTBT structureor the quad-tree structure of HEVC described above. As described above,video encoder 200 may form one or more CUs from partitioning a CTUaccording to the tree structure. Such a CU may also be referred togenerally as a “video block” or “block.”

In some examples, mode selection unit 202 may be configured to generatea coding unit for a chroma component of a block of video data in a YUV4:4:4 format or in a YUV 4:2:0 format. In this example, mode selectionunit 202 may be configured to split the coding unit for the chromacomponent into a first triangle-shaped partition and a secondtriangle-shaped partition based on enabling of a triangular predictionunit mode. Mode selection unit 202 may be configured to apply pixelblending using a set of weights for the YUV 4:2:0 format to generate apredicted block for the chroma component when the one or more processorsgenerate the coding unit for the chroma component in the YUV 4:2:0format and when the one or more processors generate the coding unit forthe chroma component in the YUV 4:4:4 format. In this way, modeselection unit 202 may use a set of weights for both the YUV 4:2:0format and the YUV 4:4:4 format, which may help to unify treatment ofdifferent chroma formats. Unifying treatment of different chroma formatsmay help to reduce codec processing overhead.

To apply pixel blending, mode selection unit 202 may be configured todetermine weighted averages, using the set of weights for the YUV 4:2:0format, of collocated motion compensated pixels of the firsttriangle-shaped partition and the second triangle-shaped partition basedon motion information of the first triangle-shaped partition and thesecond triangle-shaped partition. An example process of determiningweighted averages is explained in further detail below (e.g., see FIGS.7A-7C).

In general, in some examples, mode selection unit 202 also controls thecomponents thereof (e.g., motion estimation unit 222, motioncompensation unit 224, and intra-prediction unit 226) to generate aprediction block for a current block (e.g., a current CU, or in HEVC,the overlapping portion of a PU and a TU). For inter-prediction of acurrent block, motion estimation unit 222 may perform a motion search toidentify one or more closely matching reference blocks in one or morereference pictures (e.g., one or more previously coded pictures storedin DPB 218). In particular, motion estimation unit 222 may calculate avalue representative of how similar a potential reference block is tothe current block, e.g., according to sum of absolute difference (SAD),sum of squared differences (SSD), mean absolute difference (MAD), meansquared differences (MSD), or the like. Motion estimation unit 222 maygenerally perform these calculations using sample-by-sample differencesbetween the current block and the reference block being considered.Motion estimation unit 222 may identify a reference block having alowest value resulting from these calculations, indicating a referenceblock that most closely matches the current block.

Motion estimation unit 222 may form one or more motion vectors (MVs)that define the positions of the reference blocks in the referencepictures relative to the position of the current block in a currentpicture. Motion estimation unit 222 may then provide the motion vectorsto motion compensation unit 224. For example, for uni-directionalinter-prediction, motion estimation unit 222 may provide a single motionvector, whereas for bi-directional inter-prediction, motion estimationunit 222 may provide two motion vectors. Motion compensation unit 224may then generate a prediction block using the motion vectors. Forexample, motion compensation unit 224 may retrieve data of the referenceblock using the motion vector. As another example, if the motion vectorhas fractional sample precision, motion compensation unit 224 mayinterpolate values for the prediction block according to one or moreinterpolation filters. Moreover, for bi-directional inter-prediction,motion compensation unit 224 may retrieve data for two reference blocksidentified by respective motion vectors and combine the retrieved data,e.g., through sample-by-sample averaging or weighted averaging.

As another example, for intra-prediction, or intra-prediction coding,intra-prediction unit 226 may generate the prediction block from samplesneighboring the current block. For example, for directional modes,intra-prediction unit 226 may generally mathematically combine values ofneighboring samples and populate these calculated values in the defineddirection across the current block to produce the prediction block. Asanother example, for DC mode, intra-prediction unit 226 may calculate anaverage of the neighboring samples to the current block and generate theprediction block to include this resulting average for each sample ofthe prediction block.

Intra-prediction unit 226 may be configured to obtain unfilteredreference samples for an area of a picture. Intra-prediction unit 226may be configured to disable intra-reference sample smoothing of theunfiltered reference samples for chroma samples in a YUV 4:2:0 formatand in a YUV 4:4:4 format. When intra-reference sample smoothing isdisabled, intra-prediction unit 226 may use only unfiltered referencesamples for chroma samples. Intra-prediction unit 226 may be configuredto generate, using intra-prediction, chroma samples of a predictionblock for a block of the picture based on the unfiltered referencesamples when generating the chroma components in the YUV 4:2:0 formatand when generating the chroma components in the YUV 4:4:4 format. Thatis, for example, for chroma components in both the YUV 4:4:4 format andthe YUV 4:4:4 format, intra-prediction unit 226 may use only unfilteredreference samples for chroma samples. In this way, a complexity ofencoding and decoding video data may be reduced, which may reduce anamount of time intra-prediction unit 226 codes (e.g, encoders ordecodes) video data and/or reduce a power consumption ofintra-prediction unit 226.

Techniques described herein for disabling intra-reference samplesmoothing of the unfiltered reference samples for chroma samples may beused in combination with or separately from techniques described hereinfor generating a coding unit for chroma components in the YUV 4:2:0format. For example, intra-prediction unit 226 may be configured toobtain unfiltered reference samples for an area of a picture incombination with mode selection unit 202 generating a coding unit forchroma components of a block of video data in a YUV 4:4:4 format or in aYUV 4:2:0 format. In some examples, intra-prediction unit 226 may beconfigured to obtain unfiltered reference samples for an area of apicture in combination and mode selection unit 202 refrains fromgenerating a coding unit for chroma components of a block of video datain a YUV 4:4:4 format or in a YUV 4:2:0 format.

Mode selection unit 202 provides the prediction block to residualgeneration unit 204. Residual generation unit 204 receives a raw,uncoded version of the current block from video data memory 230 and theprediction block from mode selection unit 202. Residual generation unit204 calculates sample-by-sample differences between the current blockand the prediction block. The resulting sample-by-sample differencesdefine a residual block for the current block. In some examples,residual generation unit 204 may also determine differences betweensample values in the residual block to generate a residual block usingresidual differential pulse code modulation (RDPCM). In some examples,residual generation unit 204 may be formed using one or more subtractorcircuits that perform binary subtraction.

In examples where mode selection unit 202 partitions CUs into PUs, eachPU may be associated with a luma prediction unit and correspondingchroma prediction units. Video encoder 200 and video decoder 300 maysupport PUs having various sizes. As indicated above, the size of a CUmay refer to the size of the luma coding block of the CU and the size ofa PU may refer to the size of a luma prediction unit of the PU. Assumingthat the size of a particular CU is 2N×2N, video encoder 200 may supportPU sizes of 2N×2N or N×N for intra prediction, and symmetric PU sizes of2N×2N, 2N×N, N×2N, N×N, or similar for inter prediction. Video encoder200 and video decoder 300 may also support asymmetric partitioning forPU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

In examples where mode selection unit does not further partition a CUinto PUs, each CU may be associated with a luma coding block andcorresponding chroma coding blocks. As above, the size of a CU may referto the size of the luma coding block of the CU. The video encoder 200and video decoder 120 may support CU sizes of 2N×2N, 2N×N, or N×2N.

For other video coding techniques such as an intra-block copy modecoding, an affine-mode coding, and linear model (LM) mode coding, as fewexamples, mode selection unit 202, via respective units associated withthe coding techniques, generates a prediction block for the currentblock being encoded. In some examples, such as palette mode coding, modeselection unit 202 may not generate a prediction block, and insteadgenerate syntax elements that indicate the manner in which toreconstruct the block based on a selected palette. In such modes, modeselection unit 202 may provide these syntax elements to entropy encodingunit 220 to be encoded.

As described above, residual generation unit 204 receives the video datafor the current block and the corresponding prediction block. Residualgeneration unit 204 then generates a residual block for the currentblock. To generate the residual block, residual generation unit 204calculates sample-by-sample differences between the prediction block andthe current block.

Transform processing unit 206 applies one or more transforms to theresidual block to generate a block of transform coefficients (referredto herein as a “transform coefficient block”). Transform processing unit206 may apply various transforms to a residual block to form thetransform coefficient block. For example, transform processing unit 206may apply a discrete cosine transform (DCT), a directional transform, aKarhunen-Loeve transform (KLT), or a conceptually similar transform to aresidual block. In some examples, transform processing unit 206 mayperform multiple transforms to a residual block, e.g., a primarytransform and a secondary transform, such as a rotational transform. Insome examples, transform processing unit 206 does not apply transformsto a residual block.

Quantization unit 208 may quantize the transform coefficients in atransform coefficient block, to produce a quantized transformcoefficient block. Quantization unit 208 may quantize transformcoefficients of a transform coefficient block according to aquantization parameter (QP) value associated with the current block.Video encoder 200 (e.g., via mode selection unit 202) may adjust thedegree of quantization applied to the coefficient blocks associated withthe current block by adjusting the QP value associated with the CU.Quantization may introduce loss of information, and thus, quantizedtransform coefficients may have lower precision than the originaltransform coefficients produced by transform processing unit 206.

Inverse quantization unit 210 and inverse transform processing unit 212may apply inverse quantization and inverse transforms to a quantizedtransform coefficient block, respectively, to reconstruct a residualblock from the transform coefficient block. Reconstruction unit 214 mayproduce a reconstructed block corresponding to the current block (albeitpotentially with some degree of distortion) based on the reconstructedresidual block and a prediction block generated by mode selection unit202. For example, reconstruction unit 214 may add samples of thereconstructed residual block to corresponding samples from theprediction block generated by mode selection unit 202 to produce thereconstructed block. That is, for example, reconstruction unit 214 maycombine the predicted block and the residual block to decode anunfiltered reconstructed block for the block of video data. In someexamples, reconstruction unit 214 may store the unfiltered reconstructedblock at DPB 218.

Filter unit 216 may perform one or more filter operations onreconstructed blocks. For example, filter unit 216 may performdeblocking operations to reduce blockiness artifacts along edges of CUs.Operations of filter unit 216 may be skipped, in some examples. That is,for example, filter unit 216 may generate a filtered reconstructed blockfor the block of video data, where generating the filtered reconstructedblock comprises performing one or more filter operations on theunfiltered reconstructed block. In this example, filter unit 216 maystore the filtered reconstructed block at DPB 218.

Video encoder 200 stores reconstructed blocks in DPB 218. For instance,in examples where operations of filter unit 216 are not needed,reconstruction unit 214 may store reconstructed blocks to DPB 218. Inexamples where operations of filter unit 216 are needed, filter unit 216may store the filtered reconstructed blocks to DPB 218. Motionestimation unit 222 and motion compensation unit 224 may retrieve areference picture from DPB 218, formed from the reconstructed (andpotentially filtered) blocks, to inter-predict blocks of subsequentlyencoded pictures. In addition, intra-prediction unit 226 may usereconstructed blocks in DPB 218 of a current picture to intra-predictother blocks in the current picture.

In general, entropy encoding unit 220 may entropy encode syntax elementsreceived from other functional components of video encoder 200. Forexample, entropy encoding unit 220 may entropy encode quantizedtransform coefficient blocks from quantization unit 208. As anotherexample, entropy encoding unit 220 may entropy encode prediction syntaxelements (e.g., motion information for inter-prediction or intra-modeinformation for intra-prediction) from mode selection unit 202. Entropyencoding unit 220 may perform one or more entropy encoding operations onthe syntax elements, which are another example of video data, togenerate entropy-encoded data. For example, entropy encoding unit 220may perform a context-adaptive variable length coding (CAVLC) operation,a CABAC operation, a variable-to-variable (V2V) length coding operation,a syntax-based context-adaptive binary arithmetic coding (SBAC)operation, a Probability Interval Partitioning Entropy (PIPE) codingoperation, an Exponential-Golomb encoding operation, or another type ofentropy encoding operation on the data. In some examples, entropyencoding unit 220 may operate in bypass mode where syntax elements arenot entropy encoded.

Video encoder 200 may output a bitstream that includes the entropyencoded syntax elements needed to reconstruct blocks of a slice orpicture. In particular, entropy encoding unit 220 may output thebitstream.

The operations described above are described with respect to a block.Such description should be understood as being operations for a lumacoding block and/or chroma coding blocks. As described above, in someexamples, the luma coding block and chroma coding blocks are luma andchroma components of a CU. In some examples, the luma coding block andthe chroma coding blocks are luma and chroma components of a PU.

In some examples, operations performed with respect to a luma codingblock need not be repeated for the chroma coding blocks. As one example,operations to identify a motion vector (MV) and reference picture for aluma coding block need not be repeated for identifying a MV andreference picture for the chroma blocks. Rather, the MV for the lumacoding block may be scaled to determine the MV for the chroma blocks,and the reference picture may be the same. As another example, theintra-prediction process may be the same for the luma coding blocks andthe chroma coding blocks.

Video encoder 200 represents an example of a device configured to encodevideo data including a memory configured to store video data, and one ormore processors implemented in circuitry and configured to generate acoding unit for a chroma component of a block of video data in a YUV4:4:4 format or in a YUV 4:2:0 format. In this example, video encoder200 may be configured to split the coding unit for the chroma componentinto a first triangle-shaped partition and a second triangle-shapedpartition based on enabling of a triangular prediction unit mode. Videoencoder 200 may be configured to apply pixel blending using a set ofweights for the YUV 4:2:0 format to generate a predicted block for thechroma component when the one or more processors generate the codingunit for the chroma component in the YUV 4:2:0 format and when the oneor more processors generate the coding unit for the chroma component inthe YUV 4:4:4 format. Hence, video encoder 200 may use a set of weightsfor both the YUV 4:2:0 format and the YUV 4:4:4 format, which may helpto unify treatment of different chroma formats. Unifying treatment ofdifferent chroma formats may help to reduce codec processing overhead.To apply pixel blending, video encoder 200 may be configured todetermine weighted averages, using the set of weights for the YUV 4:2:0format, of collocated motion compensated pixels of the firsttriangle-shaped partition and the second triangle-shaped partition basedon motion information of the first triangle-shaped partition and thesecond triangle-shaped partition, respectively.

In some examples, video encoder 200 represents an example of a deviceconfigured to encode video data including a memory configured to storevideo data, and one or more processors implemented in circuitry andconfigured to obtain unfiltered reference samples for an area of apicture. In this example, video encoder 200 may be configured to disableintra-reference sample smoothing of the unfiltered reference samples forchroma samples in a YUV 4:2:0 format and in a YUV 4:4:4 format. Videoencoder 200 may be configured to generate, using intra-prediction,chroma samples of a prediction block for a block of the picture based onthe unfiltered reference samples when generating the chroma componentsin the YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format. That is, for example, for chroma components in boththe YUV 4:4:4 format and the YUV 4:4:4 format, video encoder 200 may useonly unfiltered reference samples for chroma samples. In this way, acomplexity of encoding and decoding video data may be reduced, which mayreduce an amount of time video encoder 200 codes (e.g, encoders ordecodes) video data and/or reduce a power consumption of video encoder200. Techniques described herein for disabling intra-reference samplesmoothing of the unfiltered reference samples for chroma samples may beused in combination with or separately from techniques described hereinfor generating a coding unit for chroma components in the YUV 4:2:0format.

FIG. 4 is a block diagram illustrating an example video decoder 300 thatmay perform the techniques of this disclosure. FIG. 4 is provided forpurposes of explanation and is not limiting on the techniques as broadlyexemplified and described in this disclosure. For purposes ofexplanation, this disclosure describes video decoder 300 is describedaccording to the techniques of JEM, VVC (ITU-T H.266 under development),and HEVC. However, the techniques of this disclosure may be performed byvideo coding devices that are configured to other video codingstandards.

In the example of FIG. 4, video decoder 300 includes coded picturebuffer (CPB) memory 320, entropy decoding unit 302, predictionprocessing unit 304, inverse quantization unit 306, inverse transformprocessing unit 308, reconstruction unit 310, filter unit 312, anddecoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropydecoding unit 302, prediction processing unit 304, inverse quantizationunit 306, inverse transform processing unit 308, reconstruction unit310, filter unit 312, and DPB 314 may be implemented in one or moreprocessors or in processing circuitry. Moreover, video decoder 300 mayinclude additional or alternative processors or processing circuitry toperform these and other functions.

Prediction processing unit 304 includes motion compensation unit 316 andintra-prediction unit 318. Prediction processing unit 304 may includeaddition units to perform prediction in accordance with other predictionmodes. As examples, prediction processing unit 304 may include a paletteunit, an intra-block copy unit (which may form part of motioncompensation unit 318), an affine unit, a linear model (LM) unit, or thelike. In other examples, video decoder 300 may include more, fewer, ordifferent functional components.

CPB memory 320 may store video data, such as an encoded video bitstream,to be decoded by the components of video decoder 300. The video datastored in CPB memory 320 may be obtained, for example, fromcomputer-readable medium 110 (FIG. 1). CPB memory 320 may include a CPBthat stores encoded video data (e.g., syntax elements) from an encodedvideo bitstream. Also, CPB memory 320 may store video data other thansyntax elements of a coded picture, such as temporary data representingoutputs from the various units of video decoder 300. DPB 314 generallystores decoded pictures, which video decoder 300 may output and/or useas reference video data when decoding subsequent data or pictures of theencoded video bitstream. CPB memory 320 and DPB 314 may be formed by anyof a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. CPB memory 320and DPB 314 may be provided by the same memory device or separate memorydevices. In various examples, CPB memory 320 may be on-chip with othercomponents of video decoder 300, or off-chip relative to thosecomponents.

Additionally or alternatively, in some examples, video decoder 300 mayretrieve coded video data from memory 120 (FIG. 1). That is, memory 120may store data as discussed above with CPB memory 320. Likewise, memory120 may store instructions to be executed by video decoder 300, whensome or all of the functionality of video decoder 300 is implemented insoftware to be executed by processing circuitry of video decoder 300.

The various units shown in FIG. 4 are illustrated to assist withunderstanding the operations performed by video decoder 300. The unitsmay be implemented as fixed-function circuits, programmable circuits, ora combination thereof. Similar to FIG. 3, fixed-function circuits referto circuits that provide particular functionality, and are preset on theoperations that can be performed. Programmable circuits refer tocircuits that can programmed to perform various tasks, and provideflexible functionality in the operations that can be performed. Forinstance, programmable circuits may execute software or firmware thatcause the programmable circuits to operate in the manner defined byinstructions of the software or firmware. Fixed-function circuits mayexecute software instructions (e.g., to receive parameters or outputparameters), but the types of operations that the fixed-functioncircuits perform are generally immutable. In some examples, the one ormore of the units may be distinct circuit blocks (fixed-function orprogrammable), and in some examples, the one or more units may beintegrated circuits.

Video decoder 300 may include ALUs, EFUs, digital circuits, analogcircuits, and/or programmable cores formed from programmable circuits.In examples where the operations of video decoder 300 are performed bysoftware executing on the programmable circuits, on-chip or off-chipmemory may store instructions (e.g., object code) of the software thatvideo decoder 300 receives and executes.

Entropy decoding unit 302 may receive encoded video data from the CPBand entropy decode the video data to reproduce syntax elements.Prediction processing unit 304, inverse quantization unit 306, inversetransform processing unit 308, reconstruction unit 310, and filter unit312 may generate decoded video data based on the syntax elementsextracted from the bitstream.

In general, video decoder 300 reconstructs a picture on a block-by-blockbasis. Video decoder 300 may perform a reconstruction operation on eachblock individually (where the block currently being reconstructed, i.e.,decoded, may be referred to as a “current block”).

Entropy decoding unit 302 may entropy decode syntax elements definingquantized transform coefficients of a quantized transform coefficientblock, as well as transform information, such as a quantizationparameter (QP) and/or transform mode indication(s). Inverse quantizationunit 306 may use the QP associated with the quantized transformcoefficient block to determine a degree of quantization and, likewise, adegree of inverse quantization for inverse quantization unit 306 toapply. Inverse quantization unit 306 may, for example, perform a bitwiseleft-shift operation to inverse quantize the quantized transformcoefficients. Inverse quantization unit 306 may thereby form a transformcoefficient block including transform coefficients.

After inverse quantization unit 306 forms the transform coefficientblock, inverse transform processing unit 308 may apply one or moreinverse transforms to the transform coefficient block to generate aresidual block associated with the current block. For example, inversetransform processing unit 308 may apply an inverse DCT, an inverseinteger transform, an inverse Karhunen-Loeve transform (KLT), an inverserotational transform, an inverse directional transform, or anotherinverse transform to the coefficient block.

Furthermore, prediction processing unit 304 generates a prediction blockaccording to prediction information syntax elements that were entropydecoded by entropy decoding unit 302. For example, if the predictioninformation syntax elements indicate that the current block isinter-predicted, motion compensation unit 316 may generate theprediction block. In this case, the prediction information syntaxelements may indicate a reference picture in DPB 314 from which toretrieve a reference block, as well as a motion vector identifying alocation of the reference block in the reference picture relative to thelocation of the current block in the current picture. Motioncompensation unit 316 may generally perform the inter-prediction processin a manner that is substantially similar to that described with respectto motion compensation unit 224 (FIG. 3).

In some examples, prediction processing unit 304 may be configured togenerate a coding unit for a chroma component of a block of video datain a YUV 4:4:4 format or in a YUV 4:2:0 format. In this example,prediction processing unit 304 may be configured to split the codingunit for the chroma component into a first triangle-shaped partition anda second triangle-shaped partition based on enabling of a triangularprediction unit mode. Prediction processing unit 304 may be configuredto apply pixel blending using a set of weights for the YUV 4:2:0 formatto generate a predicted block for the chroma component when predictionprocessing unit 304 generates the coding unit for chroma components inthe YUV 4:2:0 format and when prediction processing unit 304 generatesthe coding unit for chroma components in the YUV 4:4:4 format. In thisway, prediction processing unit 304 may use a set of weights for boththe YUV 4:2:0 format and the YUV 4:4:4 format, which may help to unifytreatment of different chroma formats. Unifying treatment of differentchroma formats may help to reduce codec processing overhead.

To apply pixel blending, prediction processing unit 304 may beconfigured to determine weighted averages, using the set of weights forthe YUV 4:2:0 format, of collocated motion compensated pixels of thefirst triangle-shaped partition and the second triangle-shaped partitionbased on motion information of the first triangle-shaped partition andthe second triangle-shaped partition, respectively. An example processof determining weighted averages is explained in further detail below(e.g., see FIGS. 7A-7C).

If the prediction information syntax elements indicate that the currentblock is intra-predicted, intra-prediction unit 318 may generate theprediction block according to an intra-prediction mode indicated by theprediction information syntax elements. Again, intra-prediction unit 318may generally perform the intra-prediction process in a manner that issubstantially similar to that described with respect to intra-predictionunit 226 (FIG. 3). Intra-prediction unit 318 may retrieve data ofneighboring samples to the current block from DPB 314.

In some examples, intra-prediction unit 318 may be configured to obtainunfiltered reference samples for an area of a picture. In this example,intra-prediction unit 318 may be configured to disable intra-referencesample smoothing of the unfiltered reference samples for chroma samplesin a YUV 4:2:0 format and in a YUV 4:4:4 format. When intra-referencesample smoothing is disabled, intra-prediction unit 318 may use onlyunfiltered reference samples for chroma samples. Intra-prediction unit318 may be configured to generate, using intra-prediction, chromasamples of a prediction block for a block of the picture based on theunfiltered reference samples when generating the chroma components inthe YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format. That is, for example, for chroma components in boththe YUV 4:4:4 format and the YUV 4:4:4 format, intra-prediction unit 318may use only unfiltered reference samples for chroma samples. In thisway, a complexity of encoding and decoding video data may be reduced,which may reduce an amount of time intra-prediction unit 318 codes (e.g,encoders or decodes) video data and/or reduce a power consumption ofintra-prediction unit 318.

Techniques described herein for disabling intra-reference samplesmoothing of the unfiltered reference samples for chroma samples may beused in combination with or separately from techniques described hereinfor generating a coding unit for chroma components in the YUV 4:2:0format. For example, intra-prediction unit 318 may be configured toobtain unfiltered reference samples for an area of a picture incombination with prediction processing unit 304 generating a coding unitfor chroma components of a block of video data in a YUV 4:4:4 format orin a YUV 4:2:0 format. In some examples, intra-prediction unit 318 maybe configured to obtain unfiltered reference samples for an area of apicture in combination and prediction processing unit 304 refrains fromgenerating a coding unit for chroma components of a block of video datain a YUV 4:4:4 format or in a YUV 4:2:0 format.

Reconstruction unit 310 may reconstruct the current block using theprediction block and the residual block. For example, reconstructionunit 310 may add samples of the residual block to corresponding samplesof the prediction block to reconstruct the current block.

Filter unit 312 may perform one or more filter operations onreconstructed blocks. For example, filter unit 312 may performdeblocking operations to reduce blockiness artifacts along edges of thereconstructed blocks. Operations of filter unit 312 are not necessarilyperformed in all examples.

Video decoder 300 may store the reconstructed blocks in DPB 314. Asdiscussed above, DPB 314 may provide reference information, such assamples of a current picture for intra-prediction and previously decodedpictures for subsequent motion compensation, to prediction processingunit 304. Moreover, video decoder 300 may output decoded pictures fromDPB for subsequent presentation on a display device, such as displaydevice 118 of FIG. 1.

In some examples, video decoder 300 represents an example of a deviceconfigured to encode video data including a memory configured to storevideo data, and one or more processors implemented in circuitry andconfigured to generate a coding unit for a chroma component of a blockof video data in a YUV 4:4:4 format or in a YUV 4:2:0 format. In thisexample, video decoder 300 may be configured to split the coding unitfor the chroma component into a first triangle-shaped partition and asecond triangle-shaped partition based on enabling of a triangularprediction unit mode. Video decoder 300 may be configured to apply pixelblending using a set of weights for the YUV 4:2:0 format to generate apredicted block for the chroma component when the one or more processorsgenerate the coding unit for chroma component in the YUV 4:2:0 formatand when the one or more processors generate the coding unit for thechroma component in the YUV 4:4:4 format. Hence, video decoder 300 mayuse a set of weights for both the YUV 4:2:0 format and the YUV 4:4:4format, which may help to unify treatment of different chroma formats.Unifying treatment of different chroma formats may help to reduce codecprocessing overhead. To apply pixel blending, video decoder 300 may beconfigured to determine weighted averages, using the set of weights forthe YUV 4:2:0 format, of collocated motion compensated pixels of thefirst triangle-shaped partition and the second triangle-shaped partitionbased on motion information of the first triangle-shaped partition andthe second triangle-shaped partition, respectively.

In some examples, video decoder 300 represents an example of a deviceconfigured to encode video data including a memory configured to storevideo data, and one or more processors implemented in circuitry andconfigured to obtain unfiltered reference samples for an area of apicture. In this example, video decoder 300 may be configured to disableintra-reference sample smoothing of the unfiltered reference samples forchroma samples in a YUV 4:2:0 format and in a YUV 4:4:4 format. Videodecoder 300 may be configured to generate, using intra-prediction,chroma samples of a prediction block for a block of the picture based onthe unfiltered reference samples when generating the chroma componentsin the YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format. That is, for example, for chroma components in boththe YUV 4:4:4 format and the YUV 4:4:4 format, video decoder 300 may useonly unfiltered reference samples for chroma samples. In this way, acomplexity of decoding video data may be reduced, which may reduce anamount of time video decoder 300 decodes video data and/or reduce apower consumption of video decoder 300. Techniques described herein fordisabling intra-reference sample smoothing of the unfiltered referencesamples for chroma samples may be used in combination with or separatelyfrom techniques described herein for generating a coding unit for chromacomponents in the YUV 4:2:0 format.

FIG. 5A is a conceptual diagram illustrating a first example ofsplitting a coding unit (CU) 429 into a first triangle-shaped partition433 and a second triangle-shaped partition 435 based inter prediction,in accordance with the techniques of the disclosure. In the example ofFIG. 5A, a video coder (e.g., video encoder 200 or video decoder 300)may split coding unit 429 into a first triangle-shaped partition 433 anda second triangle-shaped partition 435 when inter prediction is enabledand when triangular prediction unit mode is enabled. Examples oftriangular prediction unit mode may be found in, for example, J. Chen,Y. Ye, S. Kim, “Algorithm description for Versatile Video Coding andTest Model 4 (VTM 4)” Joint Video Exploration Team of ITU-T SG16 WP3 andISO/IEC JTC1/SC29/WG11, JVET-M1002, January 2019) and elsewhere. Forexample, based on enabling of a triangular prediction unit mode, thevideo coder may split a CU into two triangle-shaped partitions and eachof the partitions has a reference index and uni-directional motionvector. The video coder may be configured to combine the two motioncompensated partitions into a block of prediction samples and on theedge of the splitting edge, pixel blending is performed. In the exampleof FIG. 5A, first triangle-shaped partition 433 is includes anupper-right corner sample of CU 429 and second triangle-shaped partition435 includes a lower-left corner sample of CU 429.

Said differently, for example, a video coder (e.g., video encoder 200 orvideo decoder 300) may generate coding unit 429 for chroma components ofa block of video data in a YUV 4:4:4 format or in a YUV 4:2:0 format. Inthis example, the video coder may split coding unit 429 for chromacomponents into first triangle-shaped partition 433 and secondtriangle-shaped partition 435 based on enabling of a triangularprediction unit mode.

FIG. 5B is a conceptual diagram illustrating a second example ofsplitting a coding unit 431 into a first triangle-shaped partition 434and a second triangle-shaped partition 436 based inter prediction, inaccordance with the techniques of the disclosure.

For example, a video coder (e.g., video encoder 200 or video decoder300) may generate coding unit 431 for chroma components of a block ofvideo data in a YUV 4:4:4 format or in a YUV 4:2:0 format. In thisexample, the video coder may split coding unit 431 for chroma componentsinto first triangle-shaped partition 434 and second triangle-shapedpartition 436 based on enabling of a triangular prediction unit mode. Inthe example of FIG. 5B, first triangle-shaped partition 433 is arrangedon an upper left of CU 429. In the example of FIG. 55, firsttriangle-shaped partition 434 is includes an upper-left corner sample ofCU 431 and second triangle-shaped partition 435 includes a lower-rightcorner sample of CU 431.

FIG. 6 is a conceptual diagram illustrating pixel blending with one setof weights, in accordance with the techniques of the disclosure. A videocoder (e.g., video encoder 200 and/or video decoder 300) may beconfigured to perform the example pixel blending of FIG. 6 with one setof weights as shown in FIG. 6. The video coder may be configured togenerate the pixels in blending areas by, for example, weightedaveraging of the collocated motion compensated pixels based on motioninformation of the two triangular partitions. As used herein, collocatedpixels may refer to a first pixel of a first partition (e.g., a firsttriangle-shaped partition) that is positioned at a same pixel positionas a second pixel of a second partition (e.g., a second triangle-shapedpartition). Weighted averaging is further explained in FIGS. 7A-7C.

That is, for example, a video coder (e.g., video encoder 200 or videodecoder 300) may apply pixel blending using a set of weights to generatea predicted block for the chroma components of the block of video data.In this example, to apply pixel blending, the video coder may determineweighted averages, using the set of weights, of collocated motioncompensated pixels of first triangle-shaped partition (shown as “P₁”)and the second triangle-shaped partition (shown as “P₂”) based on motioninformation of the first triangle-shaped partition and the secondtriangle-shaped partition.

For example, as shown in FIG. 6, a video coder (e.g., video encoder 200or video decoder 300) may determine a pixel value P for pixels markedwith “2” of predicted block 537 for luma components and/or predictedblock 538 for luma components by calculating the respective value P foreach pixel according to EQUATION 1.

P=2/8*P ₁+6/8*P ₂   EQUATION 1

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of the first triangle-shaped partition collocated withthe respective pixel marked with “2” in this example and where P₂ is asecond reference pixel value of a second collocated motion compensatedpixel of the first triangle-shaped partition collocated with therespective pixel marked with “2” in this example.

As further shown in FIG. 6, a video coder (e.g., video encoder 200 orvideo decoder 300) may determine a pixel value P for pixels marked with“4” of predicted block 537 for luma components and/or predicted block538 for luma components by calculating the respective value P for eachpixel according to EQUATION 2.

P=4/8*P ₁+4/8*P ₂   EQUATION 2

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of the first triangle-shaped partition collocated withthe respective pixel marked with “4” in this example and where P₂ is asecond reference pixel value of a second collocated motion compensatedpixel of the first triangle-shaped partition collocated with therespective pixel marked with “4” in this example.

As further shown in FIG. 6, a video coder (e.g., video encoder 200 orvideo decoder 300) may determine a pixel value P for pixels marked with“7” of predicted block 537 for luma components and/or predicted block538 for luma components by calculating the respective value P for eachpixel according to EQUATION 3.

P=7/8*P ₁+1/8*P ₂   EQUATION 3

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of the first triangle-shaped partition collocated withthe respective pixel marked with “7” in this example and where P₂ is asecond reference pixel value of a second collocated motion compensatedpixel of the first triangle-shaped partition collocated with therespective pixel marked with “7” in this example.

The values “1” and “6” represent equations corresponding to EQUATIONS1-3. That is, a video coder (e.g., video encoder 200 or video decoder300) may determine a pixel value P for pixels marked with “1” ofpredicted block 537 for luma components and/or predicted block 538 forluma components by calculating the respective value P for each pixelaccording to EQUATION 4.

P=1/8*P ₁+7/8*P ₂   EQUATION 4

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of the first triangle-shaped partition and where P₂ isa second reference pixel value of a second collocated motion compensatedpixel of the first triangle-shaped partition.

A video coder (e.g., video encoder 200 or video decoder 300) maydetermine a pixel value P for pixels marked with “6” of predicted block537 for luma components and/or predicted block 538 for luma componentsby calculating the respective value P for each pixel according toEQUATION 5.

P=6/8*P ₁+2/8*P ₂   EQUATION 5

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of the first triangle-shaped partition and where P₂ isa second reference pixel value of a second collocated motion compensatedpixel of the first triangle-shaped partition.

While the example illustrated in FIG. 6 shows an example set of weights{7/8, 6/8, 4/8, 2/8, 1/8} for luma and {7/8, 4/8, 1/8} for chroma, otherexamples may use different weights. For example, there may be two setsof weights and in each set chroma weights and luma weights may bedefined separately:

-   -   1^(st) set: {7/8, 6/8, 4/8, 2/8, 1/8} for luma and {7/8, 4/8,        1/8} for chroma.    -   2^(nd) set: {7/8, 6/8, 5/8, 4/8, 3/8, 2/8, 1/8} for luma and        {6/8, 4/8, 2/8} for chroma.

The 2nd set of weight values (e.g., {6/8, 4/8, 2/8}) is explained withreference to FIGS. 7A-7C for example purposes only.

FIG. 7A is a conceptual diagram illustrating further details of a firsttriangle-shaped partition 639 for the pixel blending of FIG. 6, inaccordance with the techniques of the disclosure. As shown, firsttriangle-shaped partition 639 includes collocated motion compensatedpixels A, B and C of first triangle-shaped partition 639. For instance,a video coder (e.g., video encoder 200 or video decoder 300) maygenerate the collocated motion compensated pixels A, B and C of firsttriangle-shaped partition 639 using motion information (e.g., auni-directional motion vector) for first triangle-shaped partition 639.In this example, the video coder may not apply weighted averaging topixels in first pixel group 642.

FIG. 7B is a conceptual diagram illustrating further details of a secondtriangle-shaped partition 640 for the pixel blending of FIG. 6, inaccordance with the techniques of the disclosure. As shown, secondtriangle-shaped partition 640 includes collocated motion compensatedpixels A, B and C of second triangle-shaped partition 640. For instance,a video coder (e.g., video encoder 200 or video decoder 300) maygenerate the collocated motion compensated pixels A, B and C of secondtriangle-shaped partition 640 using motion information (e.g., auni-directional motion vector) for second triangle-shaped partition 640.In this example, the video coder may not apply weighted averaging topixels in second pixel group 643.

FIG. 7C is a conceptual diagram illustrating further details of a block641 formed using the pixel blending of FIG. 6, in accordance with thetechniques of the disclosure. In this example, a video coder (e.g.,video encoder 200 or video decoder 300) may determine a weighted averageof collocated motion compensated pixels of first triangle-shapedpartition 639 and second triangle-shaped partition 640 based on motioninformation of first triangle-shaped partition 639 and secondtriangle-shaped partition 640.

In the example of FIG. 7C, a video coder (e.g., video encoder 200 orvideo decoder 300) may use the 2nd set of weight values (e.g., {6/8,4/8, 2/8} for chroma). For example, the video coder may determine apixel value P of pixel ‘A’ of predicted block 641 by calculating thepixel value P according to EQUATION 6.

P=4/8*P ₁+4/8*P ₂,   EQUATION 6

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘A’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘A’ of secondtriangle-shaped partition 640 of FIG. 7B).

A video coder (e.g., video encoder 200 or video decoder 300) maydetermine a pixel value P of pixel ‘B’ of predicted block 641 bycalculating the pixel value P according to EQUATION 7.

P=2/8*P ₁+6/8*P ₂   EQUATION 7

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘B’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘B’ of secondtriangle-shaped partition 640 of FIG. 7B).

A video coder (e.g., video encoder 200 or video decoder 300) maydetermine a pixel value P of pixel ‘C’ of predicted block 641 bycalculating the pixel value P according to EQUATION 8.

P=6/8*P ₁+2/8*P ₂   EQUATION 8

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘C’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘C’ of secondtriangle-shaped partition 640 of FIG. 7B).

In some examples, a video coder (e.g., video encoder 200 or videodecoder 300) may use the 1st set of weight values (e.g., {7/8, 4/8, 1/8}for chroma). For example, the video coder may determine a pixel value Pof pixel ‘A’ of predicted block 641 by calculating the pixel value Paccording to EQUATION 9.

P=4/8*P ₁+4/8*P ₂,   EQUATION 9

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘A’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘A’ of secondtriangle-shaped partition 640 of FIG. 7B).

A video coder (e.g., video encoder 200 or video decoder 300) maydetermine a pixel value P of pixel ‘B’ of predicted block 641 bycalculating the pixel value P according to EQUATION 10.

P=1/8*P ₁+7/8*P ₂   EQUATION 10

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘B’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘B’ of secondtriangle-shaped partition 640 of FIG. 7B).

A video coder (e.g., video encoder 200 or video decoder 300) maydetermine a pixel value P of pixel ‘C’ of predicted block 641 bycalculating the pixel value P according to EQUATION 11.

P=7/8*P ₁+1/8*P ₂   EQUATION 11

where P₁ is a first reference pixel value of a first collocated motioncompensated pixel of first triangle-shaped partition 639 (e.g., ‘C’ offirst triangle-shaped partition 639 FIG. 7A) and wherein P₂ is a secondreference pixel value of a second collocated motion compensated pixel ofsecond triangle-shaped partition 640 (e.g., ‘C’ of secondtriangle-shaped partition 640 of FIG. 7B).

In some video coders, the weights of luma and chroma may be unified whenusing the YUV 4:4:4 format. As such, if a video encoder (e.g., videoencoder 200) encodes the video signal in YUV 4:4:4 format, the videocoder (e.g., video encoder 200 or video decoder 300) may be configuredto not use the chroma part of each set of weights and apply the lumapart of each set of weights to both luma and chroma edges.

In video codecs, the samples used for intra prediction may be obtainedfrom a reconstructed area of the same picture and the samples obtainedmay be smoothed by applying some filter to it to improve the quality ofprediction signal. For example, an example description of intrareference sample smoothing of HEVC can be found in J. Lainema, F.Bossen, W. Han, J. Min and K. Ugur, “Intra Coding of the HEVC Standard,”in IEEE Transactions on Circuits and Systems for Video Technology, vol.22, no. 12, pp. 1792-1801, December 2012. In some examples, videoencoder 200 or video decoder 300 may be configured to use other intrareference sample smoothing examples.

In some VVC designs, when the chroma format is YUV 4:2:0, chromacomponents will always use unfiltered reference samples. In the case ofYUV 4:4:4, however, the chroma component is subject to the same rule asluma to determine whether filtered reference samples should be used.Said differently, in some VVC designs, when chroma components are to begenerated in a YUV 4:2:0 format, video encoder 200 or video decoder 300may be configured to always use unfiltered reference samples to generatechroma components. In this example, when chroma components are to begenerated in a YUV 4:4:4 format, video encoder 200 or video decoder 300may be configured to determine whether to use unfiltered referencesamples or filtered reference samples to generate chroma components.

For example, in response to determining to enable intra-reference samplesmoothing for generating luma samples, a video coder (e.g., videoencoder 200 or video decoder 300) may be configured to perform one ormore filter operations on unfiltered reference samples to generatefiltered reference samples. In this example, the video coder may beconfigured to generate, using intra-prediction, luma samples for theblock of the picture based on the filtered reference samples. In someexamples, performing the one or more filter operations on the unfilteredreference samples may include performing one or more deblockingoperations on the unfiltered reference samples.

As such, some VVC designs may treat different chroma formats differentlyin the triangular PU mode and extra complexity is introduced to codecdesign. At the same time, the operations defined for the luma componentmay be more complex than those defined for chroma components (e.g. asshown in FIG. 6, the blending area for luma has the width of threesamples while for chroma the blending area is two samples).

In accordance with the techniques of the disclosure, a video coder(e.g., video encoder 200 or video decoder 300) may be configured tounify the treatment of chroma components for different chroma formats.For example, for triangular PU mode, the video coder (encoder 200 ordecoder 300) may be configured to use weights for YUV 4:2:0 chromacomponents instead of those for the luma component for chroma componentsof YUV 4:4:4 format. In the example of the current VVC draft, the twosets of weights that are designed for chroma components of YUV 4:2:0format are as follows:

-   -   1) {1, 4, 7}    -   2) {2, 4, 6}

In this example, a video coder (e.g., video encoder 200 or video decoder300) may be configured to handle YUV 4:4:4 chroma components and YUV4:2:0 chroma components to be the same. The video coder may beconfigured to apply combinations of these two sets of weights to YUV4:4:4 chroma components. For example, the video coder may be configuredto apply a set of weights {1, 4, 7}, a set of weights of {2, 4, 6}, or aset of weights of {1, 4, 7} and {2, 4, 6}.

Said differently, for example, a video coder (e.g., video encoder 200 orvideo decoder 300) may apply pixel blending using a set of weights forthe YUV 4:2:0 format to generate a predicted block for the chromacomponents of the block of video data when the video coder generates thecoding unit for chroma components in the YUV 4:2:0 format and when thevideo coder generates the coding unit for chroma components in the YUV4:4:4 format. In this example, the video coder may be configured toapply a set of weights {1, 4, 7}, a set of weights of {2, 4, 6}, or aset of weights of {1, 4, 7} and {2, 4, 6}.

In some examples, applying pixel blending includes determining weightedaverages as discussed in detail in FIGS. 6 and 7A-7C. For example, avideo coder (e.g., video encoder 200 or video decoder 300) may beconfigured to determine weighted averages, using the set of weights forthe YUV 4:2:0 format, of collocated motion compensated pixels of a firsttriangle-shaped partition and a second triangle-shaped partition basedon motion information of the first triangle-shaped partition and thesecond triangle-shaped partition.

An example of a weighted sample prediction process for triangle mergemode is as follows.

Inputs to this process are:

-   -   two variables nCbW and nCbH specifying the width and the height        of the current coding block,    -   two (nCbW)×(nCbH) arrays predSamplesLA and predSamplesLB,    -   a variable triangleDir specifying the partition direction,    -   a variable cIdx specifying colour component index.

-   Output of this process is the (nCbW)×(nCbH) array pbSamples of    prediction sample values.

The variable nCbR is derived as follows:

nCbR=(nCbW>nCbH) ? (nCbW/nCbH):(nCbH/nCbW)   (8-841)

The variable bitDepth is derived as follows:

-   -   If cIdx is equal to 0, bitDepth is set equal to BitDepth_(Y).        -   Otherwise, bitDepth is set equal to BitDepth_(C).

Variables shift1 and offset1 are derived as follows:

-   -   The variable shift1 is set equal to Max(5, 17−bitDepth).    -   The variable offset1 is set equal to 1<<(shift1−1).

Depending on the values of triangleDir, wS and cIdx, the predictionsamples pbSamples[x][y] with x=0 . . . nCbW−1 and y=0 . . . nCbH−1 arederived as follows:

-   -   The variable wIdx is derived as follows:        -   If cIdx is equal to 0 and triangleDir is equal to 0, the            following applies:

wIdx=(nCbW>nCbH) ? (Clip3(0, 8,(x/nCbR−y)+4)):(Clip3(0, 8,(x−y/nCbR)+4))  (8-842)

-   -   -   Otherwise, if cIdx is equal to 0 and triangleDir is equal to            1, the following applies:

wIdx=(nCbW>nCbH) ? (Clip3(0, 8,(nCbH−1−x/nCbR−y)+4)) (Clip3(0,8,(nCbW−1−x−y/nCbR)+4))   (8-843)

-   -   -   Otherwise, if cIdx is greater than 0 and triangleDir is            equal to 0, the following applies:

wIdx=(nCbW>nCbH) ? (Clip3(0, 4,(x/nCbR−y)+2)):(Clip3(0, 4,(x−y/nCbR)+2))  (8-844)

-   -   -   Otherwise (if cIdx is greater than 0 and triangleDir is            equal to 1), the following applies:

wIdx=(nCbW>nCbH) ? (Clip3(0, 4,(nCbH−1−x/nCbR−y)+2)) (Clip3(0,4,(nCbW−1−x−y/nCbR)+2))   (8-845)

-   -   The variable wValue specifying the weight of the prediction        sample is derived using wIdx and cIdx as follows:

wValue=(cIdx==0) ? Clip3(0, 8, wIdx):Clip3(0, 8, wIdx*2)   (8-846)

-   -   The prediction sample values are derived as follows:

pbSamples[x][y]=Clip3(0,(1<<bitDepth)−1,(predSamplesLA[x][y]*wValue+  (8-847)

predSamplesLB[x][y]*(8−wValue)+offset1)>>shift1)

In the above example, cIdx >0 means chroma. Additionally,wValue=clip3(0, 8, wIdx*2) is for chroma components. As such, whenwIdx=0, 1, 2, 3, 4 respectively, the wValue=8, 6, 4, 2, 0. Moreover,blended_pixel=(wValue*predLA+(8−mValue)*predLB)>>shift. As such, theblending weights used for chroma is 0, 2, 4, 6, 8 (e.g., {2, 4, 6}). Inthis example, weight 0 or 8 may refer to copying one candidate pixelinstead of blending two pixels.

In some examples, for intra prediction, a video coder (e.g., videoencoder 200 or video decoder 300) may be configured to align thebehavior of intra reference sample smoothing on chroma components of YUV4:4:4 format to that on chroma components of YUV 4:2:0 format. In thecurrent VVC draft, the intra reference sample smoothing is disabled forYUV 4:2:0 chroma components. According to some examples, video encoder200 and/or video decoder 300 may be configured to disable the intrareference sample smoothing for YUV 4:4:4 chroma components.

Said differently, for example, a video coder (e.g., video encoder 200 orvideo decoder 300) may be configured to obtain unfiltered referencesamples for an area of a picture. In this example, the video coder maybe configured to disable intra-reference sample smoothing of theunfiltered reference samples for chroma samples in a YUV 4:2:0 formatand chroma samples in a YUV 4:4:4 format. In this example, the videocoder may be configured to generate, using intra-prediction, chromasamples of a prediction block for a block of the picture based on theunfiltered reference samples both when generating the chroma componentsin the YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format.

FIG. 8 is a flowchart illustrating an example method for encoding acurrent block. The current block may comprise a current CU. Althoughdescribed with respect to video encoder 200 (FIGS. 1 and 3), it shouldbe understood that other devices may be configured to perform a methodsimilar to that of FIG. 8.

In this example, video encoder 200 initially predicts the current block(750). In some examples “current block” may be referred to herein assimply “block.” For example, video encoder 200 may form a predictionblock for the current block using unified weight information fordifferent chroma formats. In some examples, video encoder 200 maygenerate, using intra-prediction, chroma samples of a prediction blockfor a block of the picture based on the unfiltered reference sampleswhen generating the chroma components in the YUV 4:2:0 format and whengenerating the chroma components in the YUV 4:4:4 format.

Video encoder 200 may then calculate a residual block for the currentblock (752). To calculate the residual block, video encoder 200 maycalculate a difference between the original, uncoded block and theprediction block for the current block, generating a residual block.Video encoder 200 may then transform residual values of the residualblock and quantize transform coefficients (754). Next, video encoder 200may scan the quantized transform coefficients of the residual block(756). During the scan, or following the scan, video encoder 200 mayentropy encode the coefficients (758). For example, video encoder 200may encode the coefficients using CAVLC or CABAC. Video encoder 200 maythen output the entropy coded data of the block (760).

FIG. 9 is a flowchart illustrating an example method for decoding acurrent block of video data, in accordance with the techniques of thedisclosure. The current block may comprise a current CU. Althoughdescribed with respect to video decoder 300 (FIGS. 1 and 4), it shouldbe understood that other devices may be configured to perform a methodsimilar to that of FIG. 9.

Video decoder 300 may receive entropy coded data for the current block,such as entropy coded prediction information and entropy coded data forcoefficients of a residual block corresponding to the current block(870). Video decoder 300 may entropy decode the entropy coded data todetermine prediction information for the current block and to reproducecoefficients of the residual block (872).

Video decoder 300 may predict the current block (874). For example,video decoder 300 may predict the current block using unified weightinformation for different chroma formats, e.g., using an intra- orinter-prediction mode as indicated by the prediction information for thecurrent block, to calculate a prediction block for the current block. Insome examples, video decoder 300 may generate, using intra-prediction,chroma samples of a prediction block for a block of the picture based onthe unfiltered reference samples when generating the chroma componentsin the YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format.

Video decoder 300 may then inverse scan the reproduced coefficients(876), to create a block of quantized transform coefficients. Videodecoder 300 may then inverse quantize and inverse transform thecoefficients to produce a residual block (878). Video decoder 300 mayultimately decode the current block by combining the prediction blockand the residual block (880).

FIG. 10 is a flowchart illustrating an example process for pixelblending of chroma components for a block of video data with a set ofweights for a YUV 4:2:0, in accordance with the techniques of thedisclosure. Although described with respect to video encoder 200 (FIGS.1 and 3) and video decoder 300 (FIGS. 1 and 4), it should be understoodthat other devices may be configured to perform a method similar to thatof FIG. 10.

In accordance with the techniques of the disclosure, a video coder(e.g., video encoder 200 or video decoder 300) may generate a codingunit for a chroma component of a block of video data in a YUV 4:4:4format or in a YUV 4:2:0 format (982). The video coder may split thecoding unit for the chroma component into a first triangle-shapedpartition and a second triangle-shaped partition based on enabling of atriangular prediction unit mode (984).

The video coder may apply pixel blending using a set of weights for theYUV 4:2:0 format to generate a predicted block for the chroma componentwhen the one or more processors generate the coding unit for chromacomponents in the YUV 4:2:0 format and when the one or more processorsgenerate the coding unit for chroma components in the YUV 4:4:4 format(986). In some examples, to apply pixel blending, the video coder maydetermine a weighted average, using the set of weights for the YUV 4:2:0format, of collocated motion compensated pixels of the firsttriangle-shaped partition and the second triangle-shaped partition basedon motion information of the first triangle-shaped partition and thesecond triangle-shaped partition.

In examples where the video coder comprises a video decoder (e.g., videodecoder 300), the video decoder may decode a residual block for theblock of video data and combine the predicted block for the chromacomponents and the residual block to decode the block of video data. Inexamples where the video coder comprises a video encoder, the videoencoder may generate a residual block for the block of video data basedon differences between the block of video data and the predicted blockand encode the residual block.

FIG. 11 is a flowchart illustrating an example process for generatingchroma samples of a prediction block using intra-prediction. Althoughdescribed with respect to video encoder 300 (FIGS. 1 and 3) and videodecoder 300 (FIGS. 1 and 4), it should be understood that other devicesmay be configured to perform a method similar to that of FIG. 11.

In accordance with the techniques of the disclosure, a video coder(e.g., video encoder 200 or video decoder 300) may obtain unfilteredreference samples for an area of a picture (1090). In some examples, thevideo coder may disable intra-reference sample smoothing of theunfiltered reference samples for chroma samples in a YUV 4:2:0 formatand in a YUV 4:4:4 format. The video coder may generate, usingintra-prediction, chroma samples of a prediction block for a block ofthe picture based on the unfiltered reference samples when generatingthe chroma components in the YUV 4:2:0 format and when generating thechroma components in the YUV 4:4:4 format (1092).

In examples where the video coder comprises a video decoder (e.g., videodecoder 300), the video decoder may decode a residual block for theblock of video data and combine the predicted block for the chromacomponents and the residual block to decode the block of video data. Inexamples where the video coder comprises a video encoder, the videoencoder may generate a residual block for the block of video data basedon differences between the block of video data and the predicted blockand encode the residual block.

Illustrative examples of the disclosure include:

Example 1: A method of processing video data, the method comprising:determining weight information for a first chroma format; determiningweight information for a second chroma format different from the firstchroma format to correspond to the weight information for the firstchroma format; and generating prediction information based on the weightinformation for the first chroma format.

Example 2: The method of example 1, comprising: determining a mode is atriangular prediction unit (PU) mode, wherein determining weightinformation for a second chroma format is in response to determining themode is the triangular PU mode.

Example 3. The method of any combination of examples 1-2, wherein thefirst chroma format is YUV 4:2:0, wherein the second chroma format isYUV 4:4:4.

Example 4. The method of example 3, wherein the weight information forthe first chroma format is: 1) {1, 4, 7}2) {2, 4, 6}.

Example 5. The method of example 1, comprising: in response todetermining intra-prediction is applied, aligning the behavior of intrareference sample smoothing on chroma components of YUV 4:4:4 format thaton YUV 4:2:0 format.

Example 6. The method of example 5, wherein aligning comprises:disabling the intra reference sample smoothing for YUV 4:2:0 chromacomponents; and disabling the intra reference sample smoothing forYUV4:4:4 chroma components.

Example 7. The method of any of examples 1-6, wherein processingcomprises decoding.

Example 8. The method of any of examples 1-6, wherein processingcomprises encoding.

Example 9. A device for coding video data, the device comprising one ormore means for performing the method of any of examples 1-6.

Example 10. The device of example 9, wherein the one or more meanscomprise one or more processors implemented in circuitry.

Example 11. The device of any of examples 9 and 10, further comprising amemory to store the video data.

Example 12. The device of any of examples 9-11, further comprising adisplay configured to display decoded video data.

Example 13. The device of any of examples 9-12, wherein the devicecomprises one or more of a camera, a computer, a mobile device, abroadcast receiver device, or a set-top box.

Example 14. The device of any of examples 9-13, wherein the devicecomprises a video decoder.

Example 15. The device of any of examples 9-14, wherein the devicecomprises a video encoder.

Example 16. A computer-readable storage medium having stored thereoninstructions that, when executed, cause one or more processors toperform the method of any of examples 1-6.

It is to be recognized that depending on the example, certain acts orevents of any of the techniques described herein can be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,not all described acts or events are necessary for the practice of thetechniques). Moreover, in certain examples, acts or events may beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors, rather than sequentially.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the terms “processor” and “processing circuity,”as used herein may refer to any of the foregoing structures or any otherstructure suitable for implementation of the techniques describedherein. In addition, in some aspects, the functionality described hereinmay be provided within dedicated hardware and/or software modulesconfigured for encoding and decoding, or incorporated in a combinedcodec. Also, the techniques could be fully implemented in one or morecircuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of processing video data, the methodcomprising: obtaining, by one or more processors implemented incircuitry, unfiltered reference samples for an area of a picture,wherein the one or more processors are configured to disableintra-reference sample smoothing of the unfiltered reference samples forchroma samples in a YUV 4:2:0 format and in a YUV 4:4:4 format; andgenerating, by the one or more processors, using intra-prediction,chroma samples of a predicted block for a block of the picture based onthe unfiltered reference samples when generating the chroma componentsin the YUV 4:2:0 format and when generating the chroma components in theYUV 4:4:4 format.
 2. The method of claim 1, further comprising, inresponse to determining to enable intra-reference sample smoothing forgenerating luma samples: performing, by the one or more processors, oneor more filter operations on the unfiltered reference samples togenerate filtered reference samples; and generating, by the one or moreprocessors, using intra-prediction, luma samples for the block of thepicture based on the filtered reference samples.
 3. The method of claim2, wherein performing the one or more filter operations comprisesperforming one or more deblocking operations on the unfiltered referencesamples.
 4. The method of claim 1, comprising: decoding, by the one ormore processors, a residual block for the block of video data; andcombining, by the one or more processors, the predicted block and theresidual block to decode an unfiltered reconstructed block for the blockof video data.
 5. The method of claim 4, further comprising storing, bythe one or more processors, the unfiltered reconstructed block at adecoded picture buffer.
 6. The method of claim 4, further comprising:generating, by the one or more processors, a filtered reconstructedblock for the block of video data, wherein generating the filteredreconstructed block comprises performing one or more filter operationson the unfiltered reconstructed block; and storing, by the one or moreprocessors, the filtered reconstructed block at a decoded picturebuffer.
 7. The method of claim 1, comprising: generating, by the one ormore processors, a residual block for the block of video data based ondifferences between the block of video data and the predicted block; andencoding, by the one or more processors, the residual block.
 8. Themethod of claim 7, further comprising: combining, by the one or moreprocessors, the predicted block and the residual block to decode anunfiltered reconstructed block for the block of video data; and storing,by the one or more processors, the unfiltered reconstructed block at adecoded picture buffer.
 9. The method of claim 7, further comprising:combining, by the one or more processors, the predicted block and theresidual block to decode an unfiltered reconstructed block for the blockof video data; generating, by the one or more processors, a filteredreconstructed block for the block of video data, wherein generating thefiltered reconstructed block comprises performing one or more filteroperations on the unfiltered reconstructed block; and storing, by theone or more processors, the filtered reconstructed block at a decodedpicture buffer.
 10. A device for processing video data, the devicecomprising: a memory configured to store video data; and one or moreprocessors implemented in circuitry and configured to: obtain unfilteredreference samples for an area of a picture of the video data, whereinthe one or more processors are configured to disable intra-referencesample smoothing of the unfiltered reference samples for chroma samplesin a YUV 4:2:0 format and in a YUV 4:4:4 format; and generate, usingintra-prediction, chroma samples of a predicted block for a block of thepicture based on the unfiltered reference samples when generating thechroma components in the YUV 4:2:0 format and when generating the chromacomponents in the YUV 4:4:4 format.
 11. The device of claim 10, whereinthe one or more processors are further configured to, in response todetermining to enable intra-reference sample smoothing for generatingluma samples: perform one or more filter operations on the unfilteredreference samples to generate filtered reference samples; and generate,using intra-prediction, luma samples for the block of the picture basedon the filtered reference samples.
 12. The device of claim 11, wherein,to perform the one or more filter operations, the one or more processorsare configured to perform one or more deblocking operations on theunfiltered reference samples.
 13. The device of claim 10, wherein theone or more processors are further configured to: decode a residualblock for the block of video data; and combine the predicted block andthe residual block to decode an unfiltered reconstructed block for theblock of video data.
 14. The device of claim 13, wherein the one or moreprocessors are further configured to store the unfiltered reconstructedblock at a decoded picture buffer.
 15. The device of claim 13, whereinthe one or more processors are further configured to: generate afiltered reconstructed block for the block of video data, whereingenerating the filtered reconstructed block comprises performing one ormore filter operations on the unfiltered reconstructed block; and storethe filtered reconstructed block at a decoded picture buffer.
 16. Thedevice of claim 10, wherein the one or more processors are furtherconfigured to: generate a residual block for the block of video databased on differences between the block of video data and the predictedblock; and encode the residual block.
 17. The device of claim 16,wherein the one or more processors are further configured to: combinethe predicted block and the residual block to decode an unfilteredreconstructed block for the block of video data; and store theunfiltered reconstructed block at a decoded picture buffer.
 18. Thedevice of claim 16, wherein the one or more processors are furtherconfigured to: combine the predicted block and the residual block todecode an unfiltered reconstructed block for the block of video data;generate a filtered reconstructed block for the block of video data,wherein generating the filtered reconstructed block comprises performingone or more filter operations on the unfiltered reconstructed block; andstore the filtered reconstructed block at a decoded picture buffer. 19.The device of claim 10, wherein the device comprises one or more of acamera, a computer, a mobile device, a broadcast receiver device, or aset-top box.
 20. A computer-readable storage medium having storedthereon instructions that, when executed, cause one or more processorsto: obtain unfiltered reference samples for an area of a picture of thevideo data, wherein the instructions further cause the one or moreprocessors to disable intra-reference sample smoothing of the unfilteredreference samples for chroma samples in a YUV 4:2:0 format and in a YUV4:4:4 format; and generate, using intra-prediction, chroma samples of apredicted block for a block of the picture based on the unfilteredreference samples when generating the chroma components in the YUV 4:2:0format and when generating the chroma components in the YUV 4:4:4format.
 21. A device for coding video data, the device comprising: meansfor obtaining unfiltered reference samples for an area of a picture; andmeans for generating, using intra-prediction, chroma samples of apredicted block for a block of the picture based on the unfilteredreference samples when generating the chroma components in a YUV 4:2:0format and when generating the chroma components in a YUV 4:4:4 format.